I use Smart Property Systems for my property management software. 

Is anybody else using this system or are there better options?

The cost versus rent income is poor your cashflow is basically nonexistent the sellers terms really suck and you’d have a lot of risk to get the place where it needs to be .

This makes seller's less likely to go with someone using FHA versus cash/traditional mortgage.

Should the winterizing be different from the duplex which shares some pipes with an occupied unit versus the SFH vacant? 

Then consider installing a perimeter drainage system and sump pump if the bsmnt. is still wet.

If anyone insists on mailing their payment, charge a fee for "processing" the payment and definitely charge a late fee if it's not in your hands by the due date.Sign up for Cozy.co or another online rent payment system.

It would cost be $40 fee to file Writ of Restitution (for a balance of $100 on the judgement) They know how to circumvent the system very well; these are "professional tenants". 

I have spent tens of thousands of dollars on conferences and education and have developed strategies, put systems in place, and developed relationships that allowed me to have the year that I had in 2018.

Have you been able to check all the major systems (HVAC, roof, water heater, etc)?