There are some services like Guest Ranger but we do not screen in the traditional sense.Make your house rules clear and make it clear they are enforced, then they tend to screen themselves. 

Because they aren't traditional tenants in the sense with a 1 year lease and to determine fit for the house, I like to start everyone on 2-4 month leases and see how they perform.

I'm familiar with how a SFH traditionally sells, and how it is based on comps.

Creative financing: Explore seller financing or subject-to deals for your next property, which often require less upfront cash and bypass traditional lending limits.You’re on the right track thinking long-term—house hacking and leveraging your duplex are great moves.

The "slow flip" I am referring to was purchase the property in the traditional financing way and then live there while rehabbing and improving (adding bedrooms, getting the yards back in shape, updating finishes, building or adding shop space, etc.).

Tenants can be frustrating (to say the least)... and the situations that come along with them - from stopped up toilets to evictions, among many others, present challenges.I wouldn't recommend a Heloc for a long term hold as the rate is variable... and over 4 units you will require a commercial loan if going the traditional route of financing.  

Traditional lender financing with 30-year fixed loan and 25% downpayment.

When it corrects there are typically just a greater amount of opportunity especially when there was a large run up to the correction by those who did not follow traditional risk mitigation measures when investing.

Banks don't lend so little on traditional mortgage and hard money lenders don't go there , so no option for average Joe to get a qualified mortgage or for Jim the Handyman to finance it.

There's some traditional lenders in there, too.