What are solutions you have used to fix this? 

Like a barber recommending a haircut, HVAC guy a new unit...energy auditor new insulation.. pest inspector a pest treatment... insurance guy insurance....

Police harassment is the only solution to problems like this.

The solution is to figure out what else you need to buy to accommodate this.

The Communist part of the Democratic party has finally realized the end effect of not paying your rent, and they have a solution.

Driving for dollars can also be a good strategy, write the addresses of beat up houses and try to direct mail them, the more personal you can make the note and make it seem like a solution to their situation the better. 

You will have different problems, as well as different skillsets and solutions when you get further down the road.Right now, there are still great ways to make solid returns with SFH.

Other solutions?

Again, it may or may not be the way you want to go, but there are likely solutions to many of the obstacles you see.

Your going to have to spend $3500-$5500 per residence to put in a septic system for each unit or an expensive sewage treatment plant with annual upkeep...either way it's all wasted money if the city puts in public utilities in 5 years