Today would be a good day to lock in a refinance, if that's been on your 'to do' list.

What are the rules of locking in this option?

They can safely leave a window open a couple inches with the security lock inplace so they don't have to worry about a break in.

Some regulations exclude this arrangement from the codes when the owner is sharing kitchen, bath with roomers.The plus to that is if they cause problems you do not have to evict you can simply put their property on the curb and lock them out without notice.

I told USAA to lock in my rate at 3.8, they sent me paperwork via email.

I would try to lock in a fixed rate with rates expected to move up in 2018. 

Interest+depreciation+repair+etc minus rent can leave you in a negative tax condition, which could (and often is) of greater financial benefit than standing pat with locked-up equity *provided* the equity leveraged to create the interest (i.e., the mortgage on your rental) is used to make more money.

Even went so far as asking if possible, could they put  a lock box on my door to show other potential credit repair candidates.

No we don't use those as you can't place tenants in homes that have those as it could potentially trap a tenant inside during a fire.We do however use non locking handles.

If she refuses, your only option is a legal eviction.DO NOT make a bad move by changing locks, etc.