My city has finally drafted out their laws for building adus in accordance with CA law. I am looking to build a 300sqft ADU for Airbnb purposes. Luckily my street with wide enough so i do not need to have a dedicated parking spot.

I wanted to gather some insight from my fellow BP'rs. Currently I have a single family home which has been rented out to my tenants for the past 2 years and they are going on their 3rd year. My goal would be to have the ADU build which will take up half of the backyard space and the entire side yard, so that guests can enter.

I would obviously run this by them and hope that they would be willing to still stay. My questions is, how should i best present this? What can I use to make it worth their while so they stay, eg. lowering the rent? Also how much do you guys think it will roughly cost to build a 300 sqft studio like structure with a kitchen, laundry, and bathroom. 

i appreciate the help, let me know if more detail is needed. 

below are the guidelines for the adu in accordance with the city. 

A. Purpose. The purpose of this section is to establish regulations governing accessory dwelling units, in compliance with California Government Code Section 65852.2, and to provide standards for the development of accessory dwelling units (ADUs) so as to increase the supply of smaller and affordable housing while ensuring that such units remain compatible with existing neighborhoods.

B. Development Standards. Under the provisions of this section, each accessory dwelling unit shall comply with local building code for detached dwelling, as applicable, and all development standards contained in Division 3, with the following exceptions:

1. Location. ADUs are allowed on lots zoned for single-family or multi-family residential use which contain or are proposed to be developed with a single-family dwelling. ADUs may be attached, detached, or located within existing primary residence, or accessory structure.

2. Height of Structure. Height of a detached accessory dwelling unit shall not exceed the height of the associated primary dwelling unit. Any external access staircase for the ADU shall not be located at the front of the house.

3. Setbacks. An existing garage that is converted to an accessory dwelling unit may maintain the existing setback. An accessory dwelling unit that is constructed above a garage must maintain a minimum 5-foot setback.

4. Number of Dwellings. A maximum of 1 accessory dwelling unit shall be permitted on lots where legal primary single-family dwellings are allowed.

5. Dwelling Size. The floor area for an accessory dwelling unit shall not exceed 30 percent of the residential floor area of the primary dwelling or 600 square feet, whichever is less, and minimum area of 150 square feet, or as specified in Section 17958.1 of the California Health and Safety Code.

6. Number of Bedrooms. The accessory dwelling unit shall be limited to a maximum of 1 bedroom.

7. Off-Street Parking. One parking space per accessory dwelling unit shall be provided. These spaces may be provided as tandem parking on an existing driveway, or on a driveway in side yard and rear yard as permitted in Table 19.320.030-C and Table 19.320.040-D of the Zoning Ordinance.

No additional parking for the ADU is required if any one of the following conditions are met:

a. The accessory dwelling unit is located within 1/2 mile of public transit.

b. The accessory dwelling unit is located within an architecturally and historically significant historic district.

c. The accessory dwelling unit is part of (i.e., contained within) the footprint of the primary residence or an accessory building.

d. When on-street parking permits are required but not offered to the occupant of the accessory dwelling unit.

e. When there is a car share vehicle located within 1 block of the accessory dwelling unit.

8. Garage Conversion. For those ADUs created through a garage conversion which meet the criteria in subsection 7 above, the parking required for the primary dwelling unit shall be in compliance with the current parking requirements as specified in Chapter 19.336 of the Zoning Ordinance.

9. Access. The accessory dwelling unit shall utilize the same vehicular access that serves the existing main dwelling unit, unless the second unit has access from an alley contiguous to the lot. No passageway connecting the accessory dwelling unit to a street is required.

10. Way Finding. Each unit shall display address in compliance with the current California Residential Code as adopted and amended by the City.

11. Utilities. All utilities servicing the accessory dwelling unit may be metered in conjunction with the primary dwelling, in compliance with Government Code Section 65852.2(f).

12. Infrastructure. Accessory dwelling units shall not be allowed where roadways, public utilities and services are inadequate. The property owner shall provide evidence that adequate parkland, fire service, sewer, streets, and water are available for the accessory dwelling unit based on standards and thresholds established in the following:

a. 30% of Park Land Dedications and In-Lieu Fees as computed per Chapter 18.64 of Title 18 of the Buena Park City Code.

b. Compliance with all current State and local building and fire codes.

c. Compliance with Minimum Street Width – STD. 104 Standard Plans City of Buena Park Department of Public Works.

d. Sewer connection shall comply with requirements for Depth of Flow (D) versus Diameter of Pipe (d) in sewer pipe as shown below:

13. Architectural Compatibility. The accessory dwelling unit shall incorporate the same or similar architectural features, building materials, and color as the main dwelling unit on the property. These features shall include, but are not limited to, roofing material, roof design, fascia, exterior building finish, color, exterior doors and windows including, but not limited to, ratios of window dimensions (i.e., width to height) and window area to wall area, garage door, and architectural enhancements.

14. Ownership and Occupancy—Owner Occupancy Required. One of the two units shall be occupied as the primary residence of the owner of the lot. If the owner occupies neither unit, the accessory dwelling unit shall not be used as a dwelling unit, and shall not be rented.

15. Deed Restriction. Before obtaining a building permit for an approved accessory dwelling unit, the property owner shall file with the County Recorder a declaration or agreement to restrictions, containing a reference to the deed under which the property was acquired by the owner and stating that:

a. The accessory dwelling unit cannot be sold separately;

b. The accessory dwelling unit shall be considered legal only so long as either the primary residence, or the accessory dwelling unit, is occupied by the owner of record of the property;

c. Minimum rental term shall be no less than 30 days;

d. The restrictions shall be binding upon any successor in interest and ownership of the property and lack of compliance may result in legal action against the property owner to compel compliance with this section.

16. Submittal Requirements and Application Processing. Any application for an accessory dwelling unit shall include a site plan, floor plan, and elevations substantiating and evidencing compliance with all applicable development standards. Where all requirements of this section and the Buena Park City Code appear to be met, the application shall be approved ministerially without discretionary review or public hearing in accordance with the following conditions:

a. An accessory dwelling unit shall be permitted ministerially with a building permit if it is located within a Single-family Residential zone, and:

i. Is contained within the existing space of a single-family residence or accessory structure;

ii. Maintains independent exterior access from the existing residence;

iii. Side and rear setbacks are sufficient for fire safety. Fire sprinklers are not required for ADU if they are not required for the primary residence.

b. An accessory dwelling unit, which is in compliance with all applicable standards and does not meet criteria in subsection B.16.a. above, shall be reviewed ministerially pursuant to criteria listed herein.

c. An accessory dwelling unit shall be permitted with a discretionary review pursuant to Section 19.128.020 of the Zoning Ordinance (Conditional Use Permit) for those units which do not meet all applicable development standards. In no case may an accessory dwelling unit be larger than 30% of the primary dwelling unit, or be permitted where inadequate infrastructure exists.