Depends on the area for sure as to what is good and what isn't, but 25% is fairly standard.

With the right knowledge from an agent, the extra 0.5% could be worth it (and 3% is standard on a national basis). 

Whatever you find, run it by your own attorney.To answer your question, there are standard real estate contracts that you can use (though you'll probably need to modify them), and there are much simpler contracts that suffice for private sales, which is what you're doing.

I called the the office and they informed me that it was a standard charge the property manager started implementing and that I shouldn’t bother cleaning when I move out because I will be charged regardless.

Vacancies are a standard part of this business and shouldn't be discounted off of a price.  

If you want to save up 20% to get a standard mortgage then do that. 

This is fairly standard.

For example, TenantCloud.Direct deposit is a standard feature now. 

So long as it's in a good school district and close to facilities and amenities, and can get positive cash flow, you're in a good spot with it.

I found the legal wording to use by asking around within my brokerage, but there's no standard form through the Realtors Association for it so many Realtors don't know to ask their broker or have an attorney draft one.