Board members change, owners change, and the economy changes - all of which can change the owner occupant percentage, the HOA's financial health, etc. 

You could then return a good percentage of the investor capital, thereby appeasing them, and hold the asset for long term cashflow.

Typically you need 25% down for an investment property and your rate is going to be higher even if the loan is in your name, usually a full percentage point, at least.

They charge a percentage of the savings.

Can someone explain to me the different advantages and disadvantages of working at a brokerage with a percentage based commission vs flat fee?

HAHA ain't no way.On a percentage basis, you can more easily increase rent on self-storage as compared to an apartment. 

Not big numbers, but a significant percentage increase, so that's why I've been pondering this.Any insight you may have regarding this would be appreciated, but in either case, thank you for reading this little lengthy post!

What's a reasonable percentage for me to expect to retain in terms of ownership on the property?

If a row home rents for 3000 its probably going to be a lesser percentage than if it rents for 700. 

IF if is a legitimate ESA (and a large percentage are not), then you cannot deny it, or charge additional deposits or rent for it, any more than you could charge her extra for some other medical prescription such as a wheelchair or medication.