Most PM's here charge 15-20%, most are 20, but will depend on what services they offer.

Depending on the loan product, you may be able to exclude business debt once the business has paid the debt directly for 12 months.The income and losses related to the operation of the entity will affect the income side of your DTI (like Jay explained) if you own 25% or more of the entity.

Depending on the price point, they may already be running targeted ads in cities/metros for buyers that may be looking for a second home/vacation home.

If it is someone you know you can give them a straight return as if its a loan - can provide a lower interest rate to provide upside - it really depends on the lender and what are they concerned with and what is their risk profile. 

This is really going to depend on the state you are looking to do business in.

What I am saying is the tax bill for you could be wildly different depending on how long your partner has owned this property and how much depreciation they have taken.  

It really depends on where and what you are looking to do.

It will depend on the bank and their threshold / programs they are participating in. 

There is a lot of variability in this answer and, like all things in real estate, it simply depends. 

HELOCs on rentals are rare, and depends on where you are located.