This is the real estate cheat code in my opinion. 

The key is finding a property where rents cover the mortgage or, even better, cash flow.

the SBA can still work but the price point is likely going to pencil way under what seller financing would allow.

But then I was thinking to myself, the lot directly behind my current rental, in a fairly mature neighborhood, is empty. 

It is more likely if they are also investors or have investor clients.

The house is a smaller colonial with 3 beds and 1.5 baths.

That’s why lending is my biggest concern.

If the condition is similar to the market average but your rent is severely under market rate then I take an average between the current rent and the market rent and send them the following message 2 months before their lease is up (assuming you aren't in a rent control market),Dear Tenant,Some nice words and remind them that their lease is up within 2 months, please select the following options about their new lease, also mention that you are doing the best you can to maintain the rent as low as possible but with inflation, insurance and property taxes increasing, you have to raise the rent to keep up with the rising expenses. 1.

However now is the time to scale. 

that is not what sub to is.