Verifying last 2 years of rental history and income extremely important to find the “best of the worst”.

He initially said that because they were husband's wife he did not have to fill out an application and then I told him that all rental agencies in our town make them do it he grudgingly did it, but he's not said anything about his employment history and he has no current income

The income aspect is a little different though, because you will not be able to verify, or they may not show income on their application if they don't have any. 

Buying existing LTR or STR with proven income that may just need an update or a value add (add more units, add more bathrooms, beds rooms, etc.) and your next one you can try a riskier property that has less proven income.

While the new property may bring in additional monthly income, the increase in your monthly net may not justify the amount of new debt that you would be taking on.

If you get a signed lease for your rental home, your lender will be able to use that rental income as qualifying income for your loan to get your househack. 

My debt to income ratio isn’t great considering my current mortgage

I am self employed and try to minimize my W2 income. 

Has been working well from 2008 onwards till date, but you should have capital and should have alternate income to support the property expenses.

I’m a W-2 employee in a high income tax state.