

Why do you want to run an instance for that many people? Do you have 1000 people already, or is that just a number that you decided to work with? Why would people be interested in joining an instance with less functionality than the bigger ones?
Also: does it have to be Mastodon, or would you consider other alternatives? Pleroma and GoToSocial would be a lot easier to manage.
I’d guess that whoever would be willing to give you copies of legal documents just to join an “exclusive” instance would also be okay with contributing a few bucks per month to pay for its costs.