It's an okay idea, but it would honestly reduce the number of people donating for Unlimited Homes, lets assume that you use /f home (I do) and that everyone started with 2 homes, that equals 3. Why would you ever need more homes than that? In my entire time playing this server I haven't needed more. Also, the idea of being able to buy homes with in-game cash is really overpowered, it's so easy to get money on this server, would take me less than 5 mins to the get 45k you suggested and my wither farm is awful. I know people are going to disagree because they want more homes, but by a profit standpoint, the server shouldn't do it.
Pimps idea with the Enjin points is good, in a sense the server still gains something, you're forced to vote = more players = more possible future donators.
Why should it only be for NON-donors? That hardly seems fair, most of the ranks give no benefit to how much money you make, yeah you start with extra but anyone can build a wither farm. Being donor doesn't make that easier.