His has has 2 bed, 1.5 bath but has an unfinished basement which I’ll be adding 1 more room and 1 more bath.

For a 3 bed/1bath home you can easily get $1,300/mo here in Detroit.

In Florida, short-term rentals (under 6 months) are subject to a 6% state sales tax and a 6% Pinellas County Tourist Development Tax (also known as the "bed tax").

Should I put 2 beds or just one ? 

Couple of duplex 6 bed 4 bath, built in 04 and 06 sold for 160K.

I've agreed not to pay him back for 5 years.I also own a few bed and breakfasts and million dollar STRs.

For me when I'm estimating rental income I start by looking at the area for active listings <40 days old with similar characteristics to the home you're looking at purchasing (trying to find same bed/bath count, and same amenities like in CO homes with a fenced yard do very well because everyone has a dog).

We sleep 10 with 2 rooms each having 2 full beds.

a) Plum Creek, Kyle - 1900 SF, 4 bed 2 bath, corner lot, large backyard, great school district ratingb) Whisper, San Marcos - 2300 SF, 4 bed 3 bath + study room, moderate backyard, OK school district ratingThe Whisper property is about $20K higher priced.

Purchase price: $515,000 Cash invested: $128,750 Textbook quadplex buy and hold right outside the DFW metro. 2 story brick building with 4 identical 2 bed 1.5 bath units.