What software/platform is best for managing finances for investors?

You should use software to solve a problem.

I have a requirement that anyone 18 and older must fill out a separate application and undergo a background check for a fee. 

We've seen lenders charge nothing upfront apart from an appraisal fee (if its even applicable), and other lenders charge $2000+ for underwriting, processing, and other misc. fees prior to or out of closing on top of points.Second, are people finding that these fees are charged prior to closing? 

Is there a specific software/ website you use because that's one of my main challenges, finding good deals

One of those is their credit score but being below your "minimum" should be the end all be all of the application.

FYI: most PMC software includes electronic payments via ACH - for which banks charge fees past a certain amount of transactions.

Thats what I do and this lets me choose from several applicants.

It is me or does it seem like everyone says the same unfulfilling basic stuff, e.g. laws, attorneys, lease, PM software, etc.

Now if you need something called and Xactimate which is required by insurance companies to detail every thing down to the cost of each nail, this may cost you anywhere from 100-300 dollars and is usually done by a public adjuster that has the software for it, because normally the insurance company sends there adjuster and you can never trust their reports because they're trying to pay the least amount possible to the homeowner, I've had jobs where the insurance company tries to payout 20k for a job that's 70k and  if this is the case hire a public adjuster to give you real numbers that reflect the cost properly.