I would consider putting SOME money down if you've got savings Doing this would improve your DTI for future purposes and improve your cash flow and equity performance.

The price range you're looking at for 2-flats in the area is definitely on the lower end so you should be prepared for some work but what you described is a lot more problematic than making some cosmetic improvements.

We’re looking primarily at sfh for air bnb.

My strategy lately is to continue to buy, buy, buy cash flowing properties that are in areas where I see good appreciation and improvement as the years go by.

A good tenant is someone who:Has stable employment in a market segment that is very likely to be stable or improve over timeHas a credit history with which you can evaluate the likelihood that they will performPays all the rent on scheduleTakes care of the propertyDoes not cause problems with neighborsDoes not engage in illegal activities while on the propertyStays for many yearsGood tenants are the exception, not the norm.

There may be some local factors (nearby construction development or major change) influencing the owner to sell at a discount OR perhaps the owner has not been keeping up with capital improvements and the tenant base as suffered and therefore actual collections of rent have been impacted.

Secondly do a IRS Section 1031 Tax Free Exchange so that you don't have to pay the tax. 

I’m trying to buy a home from my in-laws and there selling the home to me for 100k the house value is worth at least 200-250k or more, and I plan on making improvements. 

Area is mid/high end (Washington DC) and comps all have central Air.

I just pulled a random # out of the air. after reading the little help link.