I don't look at my dojo fees as paying anyone to teach me, my sensei's teaching is not for sale, i believe. I pay fees so the lights stay on, the roof gets fixed, and toilet paper is replaced on a fairly regular basis. Who takes in the fees and pays the bills matters not to me, one dojo i belonged to it was all handled by the wife who didn't do Aikido at all (what, pay someone who didn't even DO Aikido???)---a much better choice than our sensei, by the way, whose Aikido was fantastic but whose wife had the mind for the books.
That may be the case with your sensei, or he may need the money after the divorce, she may have needed an investment, etc. Would you care if he sold it to a different person who was looking for an investment but did not do Aikido? How about a male kyu student? Why does it matter to you? For a martial art that teaches introspection, we sure seem to spend a lot of time on other's private lives.