We started out by buying light fixers and lived in them while doing the house up, and then traded up to the next.

Sell your truck on your own, don't trade it in.

And yes, parks in the markets I'm looking in, trade on a 10 cap often.As @Andriy Boychuk said, you basically value a mobile home park just like any other asset, only you focus solely on the lot rental income for the true value.

With the quality trades booked, you have holding costs to consider and if you are using a HML, that can add up quickly.Assuming you are correct with the ARV, 175K - $50K = 125K. 

Trading one debt for a higher priced debt with a variable interest rate doesn't seem like a good idea unless I'm missing something here. 

I'm more than willing to trade my time/skills to help a Mentor with their day to day activities/projects/business needs in exchange for hands on knowledge.

I'm a corporate finance analyst by trade so I immediately went looking for modeling tools and found some great work here at the FilePlace - all for free!  

I would like to trade this deal to a seasoned investor in exchange for proper mentoring specifically in the area of lease options.

You don't want to trade a property number cap for a DTI cap without realizing it.

Once she is facing real legal consequences she may change or she will leave and you can find a new tenant and be sure they know your policies about paying rent up front.