If the original balance and proceeds need to go back into the 401k, how do I make sure that I can retain my split?

We sign a joint venture agreement but the JV partner retains ownership of the property.  

It's a 1870 house and has structural issues in the foundation and retaining walls around the house.

Lucas Carl , sounds like there are some red flags and it could turn into a big commitment of your time.Since what they are asking for is more in the mentoring realm than RE agent realm, ask for a $3k-$5k retainer to see if they are serious about your time and theirs.

In Coconino county if you pay the subsequent taxes (sub taxes) then you retain your lien position - meaning if you pay the taxes for each year during the 3 year redemption period, then you can begin the tax lien foreclosure at the end of the 3 years.If you choose not to pay the sub taxes, then the county will take the lien amount you paid for your original lien, plus any interest earned, and roll that into a new lien that will also include the next year of taxes.

A portfolio loan is more of a long term traditional loan that's simply retained in house as opposed to being sold in the secondary market, at a reasonable rate, so there's no need to refi out.

I talked to my attorney about something similar whereby I owner finance a property to an Owner occupant and have property on land lease or retain partial ownership. 

Since this is a 600 amp service with SIX strands of 350mc wire the size of your thumb we had to retain the services of an engineer to draft plans along with my electrician and I figuring out how we would replace service with an occupied building.

Retain an attorney to draft if you get serious. 

We hold the utilities in our name and pay them, but provide the tenant with copies of the bills {this enables them to monitor and regulate their usage}.Every three months we reconcile the utilities budget and give the tenant the option of retaining any surplus in the budget (say for coming colder weather) or applying it to the next month's rent.