I can't even begin to describe the destruction, drug dealing, sex on the deck, etc.

Fortunately, I am dealing with convicted sex offenders who don't have much sympathy from the authorities. 

For the fish that do bite expect Trailer Park full of sex offenders with pit bulls sitting next to the car on blocks, adjacent to the failing Lagoon.In most cases you're just going to anger people by giving them a letter with a good price to find out they fit the scenario above and you're overpaying, or anger them because you're way under and they won't even contact you.This is why people don't do it.  

For example, even in the same location, insurance can vary widely based on age, sex, the company involved, any past claims, deductibles, etc etc.

Its your choice, but keep in mind that application fee's are non-refundable, so I would suggest not taking a fee from someone you know you wont rent to (due to past eviction, lack of income, etc).I would definitely recommend having thinks like rents documented (dont charge different rents for different folks), and do everything you can to avoid discriminating against anyone for a protected class (sex, race, etc). 

As far as cities around me go, most property is dirt cheap there, but was built in the 1900's. Ex

You can also check registered sex offender lists. 

Non-smoker: 10 points Number of residents does not exceed occupancy limits: (2 per bedroom+1)Background Check/Screening Name must not appear in Sex Offenders Registry.

Any thoughts on the Co-ed vs. single sex? 

Some parks tend to be "safe haven's" if you will for sex offenders, recently released convicts/felons, and people with less than legal sources of income.