How would I watch my backside on this?
I would suggest a full length mirror if you want to watch your backside. However, I don't really know what that has to do with real estate investing.
What process would I have to go through to evict the existing tenants and how much time would it take?
You would evict them using exactly the same process as any other tenant in your state, assuming you have grounds to evict them. Not having a lease is considered a month-to-month tenancy in most states and that is not a reason to evict a tenant. If you want to get rid of them, give them the appropriate notice that their tenancy is being terminated.
It's a waste of time and energy to try to qualify a tenant that is already in your unit. If they pay the rent and stay out of trouble - keep them. If not, kick them out (using the appropriate legal method).
Mike