ST Rental in IRA personal usage

Hey guys.  Big advocate of the song you sing!  I am CPA and CFP and send clients your way all the time.  I was listening to the Q&A on 8-16-22 and one question about a guy owning an interest in a fitness club (or possibly the building that the fitness club was owned in-not sure) and then he paid the normal fee to be able to be a member.  You said good as long as no funny business or special perks with his membership, he could participate just like any other member and not be a prohibited transaction.  Wondering why that would be different than owning vacation rental and paying full price to use a vacation rental owned by your IRA, etc?  I have heard you say that is a no no, so I am in the works of buying a condo in a town where my daughter lives personally (thru LLC) but if I could make that work with my solo K I would do that.  What is the difference?  Thanks in advance.  Was not excessively gratuitous to Mark so Matt will have to pick this up.  🙂  Just kidding-love you both!