They still need to come to us for any repair and we will call our normal maintenance people and if applicable we will bill them for the $100 fee.  

Good news everyone, the $500 de minimis safe harbor limit was increased to $2,500 for taxpayers who place property in service, that are NOT required to produce an audited financial statement(applicable finance statement).Effective for January 1st 2016 they are adjusting audit procedures to ignore items below this threshold provided provided you have a receipt.This means you will not have to depreciable items below this threshold as long as you elect that safe harbor.Of course it was released this morning, after I prepared for my presentation this evening.This represents HUGE $$$ savings and time savings.IRS Notice Notice 2015-82This Notice is effective for costs incurred during taxable years beginning on or after January 1, 2016.

She filled out an application and I did an online background/credit check.

You say "but I thought this was affordable housing, more like rent", aahhh yes young grasshopper, that is why we list them not by price but by averaged payment, and when they make application it is offered that they may buy said property for XYZ and than only need pay the lot rent of 123, OR, the park has "financing available" that will be an "anticipated" monthly payment of XYZ, but after the application there EXACT interest rate can be determined, also factoring what they have for a down on it. 

If they send back an application for the new tenant (the offender) by what basis can i deny his application?

Take advantage of the ability to help offset a vehicle cost, pay for your phone, home office if applicable, FUND RETIREMENT ACCOUNTS FOR YOU AND YOUR SPOUSE.

I am a software developer by profession and most of my real estate investment fund comes from creating enterprise and web applications for well known companies as a consultant. 

When they have interested applicants, they can apply with you, but you will NOT rent to them if they don't meet your written criteria. 

I would like to know what type of credit cards(Visa/MasterCard) and banks i should be looking at for opening a new card that would help report to all 3 as well as assist me in maintaining good credit.

Work with an RMLO to determine applicants ability to get credit for purchase within option expiration time frame.Until I can figure out the proper way to setup these types of transactions I will not be using them, if ever.