I don't think you have put any thought in to this. How would that solve anything exactly? If you taxed rental income at 110% then nobody would ever be a landlord, and all existing landlords would evict their tenants immediately, leaving millions homeless. Do you just want a system where you can only live in owned properties and renting is forbidden?
Do you mind sharing how big of a VPS is required to run an instance this size? One of the issues with Mastodon is that it's written in Ruby and it requires a lot of money to run a decently sized server. I'm wondering if Lemmy is more efficient given that it's written in Rust