Quote from @James Jefferson: Hi, I have a family member that had a reverse mortgage on their property it's a 3b 1b 1 acre of land heats by oil no hvac and on well water.

I do have a family friend who is currently building in my market.

Be conservative and don't rely on young adults to pay their rent.

And never let friends or family rent from you. 

I'd be looking at multiple structures. we try to build below the average new build cost in our market in Columbus Ohio which is 515,000 last year and we target land 40-50k and urban core adjacent where we get higher price per square foot. we build for clients with margin around $190 a sq ft depending on multi or single. we can get that down in our triplex it's a little higher on our single family homes because of garages and limited economies of scale. hope that helps. idk Philly but if you show me the area and styles of homes I can give you some more insights. 

Investment Info:Single-family residence buy & hold investment.

From the little I know of San Antonio (I am a wholesaler who specializing in selling STRs nationwide) its not a super hot Airbnb market but the amount you expect for rent sounds pretty conservative. 

Quote from @John Clark: Did you check for houses on the auction list,  or you can check with banks and look for REOs and convert that into a single family home and house hack or turn it into a Airbnb. 

I’m trying to buy a second multi family.

Or better said, they are vastly inferior to single family properties.- With $100K, you have a lot of options.