I do believe that you can charge an application fee regardless who is actually doing the checking.You should use a service that can give you a credit score, evictions, and criminal checks.

I think you are expecting too much from someone that wants or needs to rent in a MH park.I'd try meeting with applicants and taking a paper application.Run their background check and look at their credit score, criminal and eviction history.You may have people that get paid cash and can't produce a w2, they may not even have internet access or a bank account.I think a credit score and trying to talk to a previous landlord is the screening you need to be doing.Collect a larger deposit to give you a bigger buffer and see if you can't find some people that will turn out to be good tenants.File an evictions on the ones that are behind.

I'm aware that this is borderline criminal, sacrilegious, offensive and against everything that we've been taught as real estate investors. 

I believe with no evidence to back it up that a lot of the major crimes are between drug dealers and other criminal types.

It gave me the piece of what makes a successful person that I had been missing: dedication.Since then I'd been teaching myself coding and cyber security, working towards earning certifications.

Risks that I see are rent control (already in some places), lessoning housing regulations (there is a proposed regulation that would let any SFR be converted to a duplex, there is already ADU rules that allow an ADU to be added to most SFR, and parking requirements are constantly being reduced to allow more affordable building options), possibly at top of market (which if past history is an indicator even if Bay area is at top of market a new high will be established in no more than 8 years), potentially any number of other potential Landlord unfriendly regulations (no STRs, disallow criminal checks, rent control (already discussed), longer more onerous eviction procedures (already can take a while in some cases), mandating acceptance of Section 8 (already true in some areas), etc.).You evaluate the return versus the risks and determine if the investment appears sound. 

I have all my criminal records that I will submit to the DOJ, but just don't want to get my hopes up.

The criminal system isn't going to be much help.

We do not have much of an issue because we are up front about running a criminal and credit check. 

It should be enough to at least cover the cost of running a credit/criminal background.As a Landlord, you're trying to identify risk and then mitigate it.