I would typically avoid HOAs unless you are in a resort community and a good percentage of the homes are already vacation rentals.

Thanks again to the respective contributors, and keep 'em coming:Financing / leverage allows for faster growth.Financing allows for a much larger portfolio (for a given amount of cash), with lower positive cash flow per property but more positive cash flow overall.Having some percentage (say 50%) of properties free and clear (100% equity) can act as a backstop to protect against downturns and other bad situations.Rates are low right now so now is a good time to borrow as much as possible.Starting with cash and then quickly moving to borrowing can reduce the complexities when first starting out and building a team.Using financing leaves more cash on hand to deal with unexpected expenses.A large multi-unit benefits from economies of scale, which supports the argument to leverage existing cash to finance larger cash flow (ROI) as a percentage.One "con" for large multi-units is that the market for multi unit properties should I need to sell is tougher because of limited buyers.Gaining two or more years of proven rental revenue will be considered as good as employment income by smart lenders.This is a valuable list that I think you could almost make a book out of, with each bullet being the topic of a chapter.

Not sure whether you would end up with a high percentage of defaults.   

You charge a monthly fee based on a percentage of rent collected.

Does your friend still get his percentage? 

Mason, Blue Ash, West Chester etc are well-established markets that have a high percentage of owner occupied housing.  

Can I charge the owners by percentage or should I charge by Flat negotiated $ amount.

That means you have to run all your transactions through your broker and the broker will get a percentage of every one of them.You have to carry E&O insurance.MLS access is valuable, but ways exist to access the MLS without having a license.Now, the courses that teach using the MLS are valuable, but those are not required to get a license.Please don't take this as raining on your parade. 

"Points" are percentage of the loan.  

What would be a fair percentage for a property manager to charge me to manage my 74 lot mobile home park with 1 single family residence?