I am constantly amazed that the economy of scale with the MFU is not self apparent and given equal opportunity(meaning loan qualification for either/or), an investor would opt for SFRs instead.I am an absentee owner of a 6-plex 120miles away. 

If you are an employer and an applicant applies for a position with you and hands you their resume done via an Excel spreadsheet, verses someone who hands you a professional resume done through Microsoft Word or some Resume software program, which one would you think would be the best suited for the job, based on both applicants having the same qualifications?

If you are going to finance, it might be a good idea to get a pre-qualification letter.i do think that small MF maybe a good way to go.  

You may not discriminate as to the legal source of funds or any assistance received, including Sec 8 vouchers, so if you count income, they may qualify, obviously if Sec 8 is paying the lions share of the rents.But you can say no in the beginning.You can and probably get the basic qualifications out of the way on the phone to save yourself and the caller time.

Will getting too many pre-approal or pre-qualification affect my credit?

Do they have proper certifications to operate a PM company (state to state differences apply, but some require Real Estate Licensing and other qualifications).

This property is in a low- to middle- income neighborhood so not to stereotype but the renters tend to have lower qualifications in general than my other rental and my leasing agent forewarned me of that.

I do have criteria pre-determined and I have that in my ads :) I've been emailing those who are interested my minimum qualifications first, letting them know that I don't want them to lose money on the application fee if they don't qualify.   

This second email also goes into detail about our qualifications, required verified income, and total move-in monies needed.  

And if you've received 50 calls, you should have at least some other qualifed applicants.