I am sure there are standards (which others can comment on) however at the end, you have to give him enough of what he wants and he has to give you enough what you want to get the deal done.I suggest that you write down how you want the arrangement to be laid out, then talk to him with the goal of seeing if he is interested.

You must do your due diligence to find a good deal, but they are out there.You should connect with @Kerry Smith, he moved to JBLM about 1 year ago and is currently house hacking a duplex as I write this.

In the long run...especially after taking into account all the tax write offs...it's a no brainer for me.

So write down a few specific questions you have, but then just try and make friends with the guy.

At that point you have a general partnership and 1065 obligation.If you're doing that, it may be advantageous to take it one step further, form an LLC and write your mother into the operating agreement as the functional equivalent of a limited partner. 

@Lacie Gilbert Great morning,I am not a tax professional by any means but I think she would write off the the money she paid to you as rehab expenses, maybe issue you a 1099 at the end of the year.

Pretty much any local lawyer should be able to help you but most the people I used to work with would probably be able to write you a clean operating agreement cheaper than reviewing one you wrote. 

(Perhaps I need to write a new post on how to use Google?)

It should always be in writing.

I certainly did not, and neither did the mortgage lender who  pre-qualified me.After closing on the HELOC  this week, I was reading through the docs last night and stumbled upon the Occupancy clause :"Borrower shall occupy, establish, and use the Property as Borrower's principal residence within 60 days after the execution of this Security Instrument and shall continue to occupy the Property as Borrower's principal residence for at least one year after the date of occupancy, unless Lender otherwise agrees in writing, which consent shall not be unreasonably withheld, or unless extenuating circumstances exist which are beyond Borrower's control"So I'm not sure what to do.