adding / creating mother-in-law suit at personal residence

8 Replies

BP,  My fiance and I are looking to buy our first home!!! To make our new home work for us we want to look into building or convert a garage into a mother in law suit. A little variation of house hacking @Brandon Turner ;) Has anyone done this and what are some estimation for cost, tips, and/or thoughts?

Hey @Walter Pape- I actually did that once, turned an area above my garage into a rental, and rented it to my brother in law, who moved in a bunch of friends. 

Was not a good experience :) 

That said, I was young and dumb and made lots of mistakes. I've since turned it into just 'part of the house' and rent the whole thing out to someone. 

I'm also looking potentially at moving to Hawaii, and buying a house with a mother-in-law suite, living in that, and renting the main house out as a Vacation Rental. We'll see ;)

We bought our current home with the plan of renting out the finished basement.  It works fantastic, since the basement is essentially an entire house, with 9 foot ceilings, full bath, a bar that has the amenities of a kitchen (no stove, but college kids rarely use stoves), and a big bedroom and living room. I can't speak to the costs of ADDING a mother-in-law suite, but it may be simpler to find a house that lends itself to creating a mother in law suite without much rehab, e.g. a walkout basement, existing wing separate from house, master bedroom with door to outside (separate entrance), etc.  Good luck!

Our first home purchase had a legal basement apartment. It was like house hacking but better than just half of a duplex. We still had 2400 sq ft on the main floor and upstairs for our family (which includes several kids).

Our neighbors built an apartment above their garage. The apartment is very nice and even though it is small they don't have trouble renting it out because it is so nice. gets so hot in the summer! They have had a problem keeping renters and most of them say it was the heat that drove them away.  So while I don't know costs you will want to pay special attention to insulation to control the temperature (especially in Florida).

I completed a similar project 6 months back, but in our case it was converting the basement/ground_level floor of a highwater bungalow into an inlaws quarters. So far, it has been a very positive experience.


  • Don't underestimate the cost of running electrical, gas, and plumbing which will probably be necessary for a new kitchen and bathroom. These trades cost a lot.
  • Don't under estimate the cost of the kitchen and a bathroom overall.
  • Make sure the cost of the two above things justify the extra income.
  • Think about resale value. What might a future home buyer want? Can the apartment design also function as a game room? hobbie kitchen? man cave? Or will it be more of a resale liability?
  • What are permits zoning your area?
  • Do you want to deal with a tenant in your own 'home' per say. Will you be renting to strangers?
  • For concrete floors, consider LVP.
  • For heat/AC, if needed, look into ductless heat pumps
  • For appliances, consider upgrading the main house, and moving the old appliances into the add on.

In our situation, we spent about 10k, doing a lot of the work ourselves, but rent is 1000/month with all utilities covered. The previous owner had already done a half hearted build out based on previous improvements. Lucky for us, he was too cheap to do it correctly, else the purchase price would have been much higher. It did have a functional bathroom (minus some new paint), and new ductless heat pumps. We had to install the floors (LVP), a full kitchen, (although it was plumbed already), closets, new lighting, and moving some walls and doors for a better layout.

We already had renters lined up before we purchased the place, as we had multiple friends who might be interested. We walked them through the house before signing the papers, to get a good sanity check that our vision matched our potential customer base. We put in a higher quality kitchen than a typical basement apartment would have, which costs more, but makes a big impact on appearance. We toured multiple places where the owners had attempted such conversions, and the kitchen was always where the corners were cut. Our final design made it such that the property can easily function as one large house with an entertaining or hobby kitchen downstairs, or as two separate units. We put a lot of thought into how we would want to use the space if it wasn't rented out. The biggest unexpected sticker shock was having to pay a plumber ~800 just to run the gas line 10 feet.

@Walter Pape Remember, in some areas, a 4/2 is cheaper than 3/2. So the 4th bedroom might be used instead of the garage. Just a thought. :)

We just completed a garage renovation to a full 1BR / 1BA apartment in December 2014. Our house happened to lend itself well to this because we had a downstairs hallway with a full bath and bedroom going right out to the garage. We don't put our cars in the garage and it was full of stuff we never used anyway. We estimated 4 weeks which turned into almost 9 months for a variety of reasons - however it turned out great and the rent pays our mortgage. It cost more than we budgeted (partially our fault, but not fully) but it was a great experience. If I could find a house in the area with the same layout I would do it again but it's tough where we live. I think the posters above covered most of the things you need to look out for. We always opt to go with higher-end finishes and designs than competitive offerings in all our rentals and we get great tenants and fill them quickly (it pays off in the long run). This one took less than 24 hrs. to rent and so far the tenants are ideal.

Where we live it is $350/sq. ft. to build so it's not cheap to renovate either. I have no idea what it costs in Florida but you should be able to find that pretty easily. One mistake we made was to contract out some of the work, and do some ourselves. That slowed things down and messed up coordination in some cases (we are busy and travel, etc.). 

Some things we did that worked out well:

Upgraded our in-line hot water heater. Separated the electrical for the rental and installed radiant heaters (super efficient and cost-effective for tenants ), no need for A/C as it stays at about 68 in the unit all the time w/o heat. Used higher-grade sheetrock for sound isolation, It's a bit more expensive but worth it. Upgraded appliances, fixtures, flooring, etc. We asked for absolute top-of-market rent (higher than many 2 BR units) and got it right away - housing is really tight here so that may not apply in Florida.

Good luck and based on our experience we do it again in a heartbeat.


You may want to check with your local zoning department and inquire about permitted uses in. There are areas where a second kitchen is no allowed or a variance may be required. 

@Brandon Turner

 Really interested to see how it turns out, are you the next Panama Matt? 

@Walter Pape

I am looking at an 8 bed, 2 flat tomorrow with a advertised "basement mother-in-law suite". Zoning shows R3 (two family residence). This deal will only make sense if I can figure out how to get it rezoned as R4 (Limited General Residence) and split the basement as a legal unit. Definitely look into zoning as others have suggested. I haven't experienced what happens with zoning violations, but I'd prefer not to find out.

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