Most of us had to be this ourselves (with a little help from our investor agents, where applicable).

I am above 50% on standard Visa/MC, below 50% on Amex, and about 0% with anything that is like a local credit unions. 

I feel like it would be great to trust a property management company on all of this, but it would be hard not to step in if you could do a better job at screening bad tenants (eg screening HUGE future problems).I initially managed properties myself, but now I delegate that responsibility to my business partner, personal assistant, or a property manager at my brokerage.Most PMs I know will send you an applicant for final approval and you can get on the phone with them and ask them questions

To receive the 4% ratio, you have to submit an application showing the property is your primary residence.

Most lenders will use the middle of your three credit scores and if there's more than one applicant, the lender will go with the lower of the two credit scores.

Review the quality of the tenant base (do they have a history of paying on time, what were the original screening criteria, do they have applications on file).

The only issue is with a bit lower rent there's a higher number of applicants that won't qualify but I don't mind the volume to get it filled. 

Is your DSCR ratio greater than 1-meaning are you cash flowing (according to the lender's criteria of mortgage, property taxes and insurance (and HOA) if applicable).

(Do you really want an applicant who can and wants to move in tomorrow?

Your accountant will do it for you at tax time if applicable.