Resident wants to buy a second home in park while putting 1st up for sale

I have a current resident who owns their home and want to upgrade. Another ex-resident has a nice home for sale in our park and the two of them made a deal. Then the current resident came to me. I’m not sure how to handle this situation because I’m new. Here it is:

A married, dual income couple in the park owns their home free and clear but wants to upgrade. They saw another home in our park for sale by a private resident and wanted to grab it before someone else did, so they signed a contract to buy the home from the seller for $4,000 ($200 per month for 20 months). Their plan is to move into it and then sell the first home.

The couple makes a combined $2,658 per month gross income before taxes, and have no children to support as far as I know.

If they rent two lots at roughly $350 per month each with the base water/sewer factored in they are at $700 / month. Add in the payment to the private seller we are at $900 / month.

I do believe their first house will sell quickly, but there are many “what if’s”

What if they can’t afford two lot rents one month - can I evict them out of the park completely for not paying only one of the two rents? What happens if they miss a payment to the owner of the house they buy? Etc.?

They are quiet, good residents and I want them to be happy and get this house but I’m nervous about them owning two and the results of a financial misstep.

In the mean time I have cautioned them not to make any payments to the first gentleman because they haven’t been approved for the second lot lease yet, and to just sit tight.