Sometimes it's better to pay a bit more, for a real professional to handle your most important transaction. 

For small MFH/SFH you have to find the deal, inspect, estimates and decide what to do, make a deal, get financing, get contractors, manage contractors, pay contractors, then turn it over to a property manager.

You let it slide, waive the late fee, and she pays by the 10th.

The long term (since 2000) appreciation for chicago is 3.35%/year.  3.35 * (10/6) = 5.58% return from appreciation.Total return: 5.58% (appreeciation including the leerage) + 2% (cash flow)= 8.58% + equity pay down + tax benefits.I fear your total return does not justify the effort and risk of residential RE.San Diego is a good market for long holds.

Keep in mind if you buy another primary residence, you'd have better rates, terms and can pay as little as 5% down for multi family up to 4 units.

My ADU is under 500 sq ft, so I didn't have to pay the extra sewer connection and school fees.

As @Dan H. has stated building and ADU can take a while to pay off and could affect the appreciation on the exit sale without a garage which could limit your sales to another investor. 

Long Term non-paying Tenants.

If you can buy a 4 flex that will allow your tenants to pay most if not all your mortgage. 

It will pay off.