It all depends on where you're looking, the type of property, what our goals are, and how do you sound and what your credit score is but the paper analysis and the package you give them and who they are.  

I explained exactly what I wanted the loan for (debt consolidation) and that my credit score was going to be in the mid to upper 6's because of it.

Joey,When you run into a non-investor with an 800+ credit score and a pre-approval for 400k you will do the deal

We have been very strict adhering to a minimum of a 640 credit score for applicant and 3 months rent in gross income but we are struggling to get tenants for our properties.

Other than a minimum credit score what other specific stipulations can I legally make to help get the best tenant possible?

With a 30 day timeline your options are quite limited.Assuming your zoning is some version of Agg then here are my suggestions on options to pursue.

I may be able to qualify for a personal line of credit based on a credit score over 800 and strong income from my W2 job, but the amount properties sell for in my area would require a rather high amount for a personal line.

I don't like old lists lasting forever on BP, so my solution is just to email the current version to people if they want it.

This creates some added value too as the right one will offer your tenants additional capabilities (ie. their ability to report their on-time rent payments to the credit bureaus as a way of building their credit scores, which can create an added incentive for making sure they pay that rent on time).

Personally I would prefer a simple manual version myself, but I'm sure many would like the convenience of a remote controlled option.