How are you advertising your rental? 

It's a common tactic used by get-rich-quick gurus.Some options do exist but they are difficult and rare.

This is less common with big banks (but doable), and more common with smaller or local banks. 2.

What is the common thing that doesn’t pass the inspection?

They are advertising a rate as low as 3.5% for the HELOC, which is lower than the 5 or 5.5% rates I have seen elsewhere. 

I give them a safe, comfortable home that lives up to the advertisement and treat them honestly and fairly.

Results may vary, but the most common thing to do is keep it in your personal name for 6-12 months and get a cash out re-fi through a regular bank.

You will also want to understand common area maintenance, especially if you are targeting 3 units or more (lawn care, snow removal, cleaning and upkeep of common areas, etc) and understand the parking situation.

(In general, in my anecdotal experience, going from a "greater" zoning use, like R2 which is the common designation for a duplex in my area, to R1, which is the common designation for a SFR in my area, is easy and automatic.

Advertise it everywhere, FB, CL, emails to buyers of this type of property, friends, family... obviously make sure you are advertising it legally.