The main consideration I believe is missing is the cost of the hardware where you will be hosting the server. Maybe you have a old computer lying around, in that case its not an issue of course. By the way 25$ per month seems a bit expensive, there are probably cheaper alternatives, just for the sake of comparison.

Hi, I think localAi is a good place to start.

You could also check out Conduit, it’s still in beta but very lightweight.

Conduit is a lightweight open-source server implementation of the Matrix Specification with a focus on easy setup and low system requirements. That means you can make your own Conduit setup in just a few minutes.