And insurance will vary depending on size of house and environmental factors, but compared to all the other expenses it would be so nominal of a percentage.The only thing that is not included in the standard 70-80% formula, is your personal and or corporate income tax rate.

I've been looking at the concept of hiring a real estate agent to act as the broker in charge for a nominal fee.

We've got a nominal base tax rate on rental income way higher than 15%, but you have the option of picking your effective actual tax rate on rental income by spending as much (or as little) of that rental income on improving and maintaining your property as you wish!

On this point you're 1. incorrect about prices increasing and 2. looking at nominal prices not real prices.  

There is no required amount by law but most states want to see some form of amount great that a nominal amount of $1 or $10.6.

@Marisa R.I think if it's a Warren or Bernie nomination then RE investors need to beware; not right away but looking out 10-20 years there may be enough credibility granted (assumed) by most people to some of what they're advocating to slowly move the needle on what people are willing to entertain.  

Then add in the nominal value of the MHs.  

They let you do a dozen or so before they want to start charging you a nominal fee. 

I only considered the nominal price increases you might expect as an investor.

Yes, there will be a nominal annual fee, but comparing with SDIRA you can eliminate all transactions and asset-based fees associated with the IRA custodian.