Unlikely.80% of our landlords use Excel or bar napkins or some combo. 60% of our small business owners are single-shingle "one man bands," and they too use Excel.QBO, Waveapps, Freshbooks, Stalebooks, SloppyBooks, Xero, One and all the others are nice to have but not must haves until you have several rentals or complex rentals (such as a strip mall or something).

I chuckled at first but I think Jerry W. is onto something by suggesting you buy additional properties and partner with this creative individual, as long as it is okay with your city to begin with.Airbnb requires the place to be in good working and sanitary condition as.

After researching online I found landlord responsibility under California Civil Code section 1941 described as followsClean and sanitary buildings, grounds and appurtenances (for example, a garden or adetached garage) which are free from debris, filth, rubbish, garbage, rodents andvermin. 

I'll try to present a basic plan with some napkin math soon.

Obviously there's a lot I don't know about your deal, but using napkin math and your figures, Id go for it - I think $1600-1800/month is realistic depending on the area at that valuation (just guesstimating the neighborhood quality based on ARV).

The data on cap rates in my investing area are moving around but last year's and now are in the same league.So that seems like good back of the napkin analysis for me now.

Based on the limited info - back of the napkin says not to go any further on the duplex you're looking at unless you have deep pockets to carry it while you wait for the capital gain.

I am also new to investing but from what I understand the 2% rule and 50% rule are more of "guidelines" and don't work in every market.Here is a good post about crunching the numbers.Rental Property Numbers so Easy You Can Calculate Them on a Napkin

It had everything down to the napkins, silverware, etc.

If plenty of suitable land is available for a repair/replacement/expansion system, this may not be too big a deal ($1k-$3k), but if not (and sanitary sewer is not available) - a repair solution could run $5-$20k for a pumped or on-site treatment system.