I'm looking to start a WordPress hosting business for a specific genre. I want to use WP Multisite to allow users to have a quick & instant sign-up. However, I'm concerned that all users will be sharing the same database. Wouldn't that database get too large over time? Is there a way to put, say 50 users on one database and then 50 on another? Or will multi-site not be the best solution for my business?