My buddy is that rare breed of guy who actually pays far more than the court-ordered amounts, like clockwork, to his ex-wife so that his daughter can be well cared for. 

If your relatively young and your roommates are good buddies I wouldn't worry about them moving out.  

I have one buddy who has triplets and his wife works full time so he does a lot of kid duty and  he made I think 220k last year on commissions...

IE an apartment.. but for the urban dweller they can rent those for 800 to 1200 a month so a nice income on your exisiting sfr.One of my buddies is contemplating building a developemetn of them in Roseburg Oregon he owns quite a bit of acreage there  and in our state every parcel has zoning period .. so this is a project that has to go through the subdivision map act.but in Oregon they embrace small lots.. ie 1 to 1500 sq ft lots are common.

You don't have to buy an apartment building right out of the gate- house hack and rent to your buddies.

http://www.relevantbuildings.com/  check out these ... my buddy in Oregon has launched these.. not sure about the SFR ones but I think the multi family has some promise in high value land markets..

BRRR is our primary strategy.Good luck buddy.

I currently work  with my buddy doing small residential remodels.

Buddy has a house in 'squan, and I told him to AirBnB it, but he was worried about raucous guests.  

If I had an extra $20,000 I would partner up with one of my real estate buddies that have 100+ units and shadow them on the deal.