Go to a local credit union.

Should I start with any credit union or Lendingtree.com etc or any other source?

And you're probably going to pay 3 points or so upfront for that hypothetical hard money 2nd mortgage on an investment property to 70% CLTV, assuming you could get it.I don't have any credit reports in front of me, but I'm pretty sure you can do a little better than 4.83% at a cost of three points.

Along with a credit report, I have read that other documents for a rental application should be included.

I have 750+ credit and zero other payments. 

If you want to manage it yourself, get a merchant account set up so you can take credit cards and plan on spending the $800/yr on HomeAway or VRBO to be included in searches.

I like the part that when they pay on time, it helps them build their credit.

I ended up paying the HOA fees with the additional costs of the collections company - totalled at $6700 (the fees themselves would have been $4000) A couple of years ago they lease the condo to couple due to the wife's high credit rating.

@Andre Minasyan,He mentions the supply vs demand issue.He did not mention the factors which are currently dampening demand.Lending is still quite dear, though there has been some improvement.

Unfortunately we have to start from scratch with the credit profile with neither of us having lived here before.