And to add on to Greg's point, certain tenants will quickly move over, others you may have to incentivize (if that's something you want to do), and the rest you will have to non-renew leases and rehab the home for resale to someone new.
You can do the conversions in three months reasonably - it's really just a paperwork exercise. Be sure before you convert these people over to owners they can afford to and are committed to make the external improvements to the homes needed to meet your reasonable Park rules. There's nothing worse than making a renter an owner, and then they won't (or don't have the money) to repair their home and you end up evicting them shortly after.
The POH repair budget should really be quite minimal, and really should be a focus on how many homes do I expect to rehab for resale. For each home you just need to estimate how much it would take to get it in sellable condition, and then make some assumptions about the number of tenants you expect to convert versus remove in those POH's (e.g. ask during the tenant interviews during diligence to get a rough estimate).
Rehabbing a number of homes will obviously take more time than 3 months unless you have a good established contractor pool in place.