I like to be able to compare my expenses by category to my total income (percentage of income) for the month to make sure my spending habits don't change (although I don't mind when my savings percentage increases). 

Are there certain percentages that people usually go by?

They also get a flat fee every month for management, not a percentage of rent collected, so they make more money if they put bad tenants in my property, which strikes me as a huge conflict of interest.

They are allowed a general conditions percentage (10-15%) for insurance, fuel, car insurance, builder's license, etc. as well as a profit mark-up (usually 5-15% depending on your agreement with them).  

So being an employee or even getting paid as an independent contractor working on a percentage basis for projects can be a good way to "get your foot in the door" of the business, without learning it all the hard way.I recommend against getting started and learning form your mistakes. 

I would think, though, that it would be more a percentage of tenant usage. ie Tenants used the property for 60% of your lease term for the rental so $15,000 * .6 = $9000 deduction.

The guide indicates that this would be "damage," but nonetheless says that the tenant is only responsible for the replacement cost multiplied by the remaining useful life percentage.  

The owner will not have to deal with a realtor thus saving a large percentage of realtor's fees.

We recently used them....called the toll free number on the post card beginning of december....spoke to a Larry.....later called said our credit score was lower than what the terms were but said no problem they can just up the percentage so that is what we did.  

Just my opinion, but unless you can find an investment guaranteed to make you a higher percentage than your current loan rates, Prosper or student loans, it is better to pay down the debt, although I am not sure about that Prosper loan and if it has prepayment penalties, which would have to be considered.