I agree with Ray—condos, especially with the new reserve requirements and reassessments, are becoming pretty unaffordable.

If you meet that requirement, I highly recommend it. 

Most hard money lenders require 10-20% down payment of the purchase price or total project cost.Holding Costs During Rehab: Yes, you'll need to cover carrying costs, including hard money interest, utilities, taxes, and insurance.

That is often a matter of opinion and will depend on the attitude of your municipality.Most municipalities do not require neighborhood approval, but will offer the public opportunities to provide input which will be considered.

Make sure to get legal advice on what you can and can’t do for bill back and what kind of notice period is required in your state. 

What documents do they require, what credit scores do they allow, how do they verify previous rental history, etc.?

To vet guests, you can use a pre-booking form, ask about their plans, and require an ID and signed agreement.

Bought 2 SFRs on the same lot that are zoned commercial (found on Crexi) for less than the price of a normal SFR because of the value add required (like kitchens and full baths, lol), but should BRRRR nicely based on the LTR and STR projections. 

The fix/flip might be a good way to get such a relationship started: usually has lower cash out of pocket requirements and you can sell the property faster to recoup the capital invested, plus any profits.

However, you can't sell something unstable, with circular references, requiring human override, etc.But, if you stabilized it, the model loses efficiency.