I worry about blowing all of my mother's retirement assets, even though my mother would like to invest this equity.What would you do in my situation?

If the deal is right, I could retire on the income.

He just wants a guaranteed sale, about a year from now, with a closing date of his choice, so he an his wife can retire and move into their second home.It's a single family 3/1 that's been his (and his wife's) primary residence since 1995, well maintained, with some upgrades. 

However, any retirement contributions you want to make are generally limited by the amount of the W-2 income you are taking whereas an LLC member can make retirement contributions based on their entire LLC income.  

I am on permanent Federal Disability Retirement and can easily afford the monthly payments.Thanks everyone.

The other is a fourplex owned by a guy looking to retire.

However if I was closer to retirement I would look more into paying them down unless I found an incredible property.Elliot

My hope is we time the market then to purchase and then ride the organic appreciation cycle to eventually CF rental or sell and invest in the South where we plan to retire anyway. 

Learn, Learn, and oh yeah learn.Eventually at one point I will be a full time Real Estate Investor and retire my wife at first then retire my self.Business Plan:Keep my day job (Architectural Drafter / Project Manager at an Architect & Construction company) Start in Wholesaling (Part Time) to build my knowledge of  finding the deals and create my network of investors, contractors, property managers, etc... and absorb my self in my market.Move to purchasing my own great deal and having a few wholesalers in my network to provide me further leads. still keeping my day job...

Why do you want to put RE into your retirement plan??