@Naoko PottsThis type of request is a luxury, not something that will prevent them from using the property.

The option agreement is what gives one the option to buy the home without being obligated to purchasing it3- more involved process than simply signing a lease or a purchase agreementIf your main objective is to prevent breaking a lease, finding a property with "month to month" leasing may be your best bet. 

The only good a judgement does is when it is recorded it can prevent the defendant from getting a loan, or selling their house. 

I'm looking for preventative maintenance to make sure things last as long as they can.

If so, what prevents them from continuing to pay the rent and never paying the plumbing charge?

I will suggest you get a HELOC on your primary residence so you have access to the cash reserve for when you need it. hold off on getting the 401k loan till you actually need it. most likely the townhouse will rent fairly quickly except if there are extenuating circumstance which will prevent it from g listed as a rental on the market immediately after

You should have a penalty for breaking the lease early and that penalty should be significant enough to prevent any loss and compensate you for your time and trouble.

Make sure the refi does not prevent you from qualifying on the new home purchase.   

They prevent the Solo 401k participant (as well as other disqualified persons such as some family members) from transacting with or benefitting from the investments of the Solo 401k.

Having separate legal entities doesn't per se prevent you from making a distribution from one and a follow on contribution to another.