And since it's not a firm amount for a set number of payments, it won't be coded like a mortgage, but often it's coded like a credit card. 

That's what I also came to the conclusion too after reading through further IRS code.

all my properties are in the 61104 area code 

It is very important that you calculate right metrics in the right way..else you can get stuck with a wrong deal....Zip code is a too large of an area from RE perspective.

You can filter the data by zip codes you want to buy in and when the homeowner purchased their home.

I'm not familiar with the codes in your city/ town.

@Eugene Kemp I did check the Texas Property Code on this topic and there doesn't seem to be anything stating a particular limit on the late fee you can charge. 

Thanks for doing that, its easy to talk about it but the proof is in the pudding.C3 would be its classification code on condition.

It took them 2 years to build their home from being given all sorts of grief by water/sewer, zoning and codes.

So, it you do pursue this, I would say include at least the basic utilities, and  possibly consider including internet/cable as well.Also, double check your local codes- where we are, no more than 3 unrelated adults may live together without specific zoning.