I suggest you hire an appraiser to get a professional opinion.

I don't think taking the lockbox off will help you - it's much easier to pick the actual lock, than cracking the LB open.You won't be able to meet the scammers, they will ask you to mail money.. 

Professional management of the property is currently in place and can stay in place after the sale making for a smooth transition.

These are professionals with additional training and a stricter code of ethics.

Scott's book an estimating rehab cost, it is very clear and helpful to anybody.It will tell you what to ask to contractors, find out your local prices by talking to contractors.Then find an agent, go check houses, look at the list, decide what needs to be done.Your agent should provide you comps, so you know if price is good or bad.If everything is greek to you, you might want to start by getting professional help as much as networking.Good Luck!!!

There are also several other experienced tax professionals who specialize working with real estate investors, they might not be local to you but most of them will work with clients remotely.

If that doesn't work then meet with the tenants after the sale and go through the lease, be nice and professional, and let them know you are going to improve things but be firm on the terms of the lease. 

These are professionals with additional training and a stricter code of ethics.

Every person considering a monetized installment sale should obtain tax and legal review from an objective, professional, third-party adviser.

These are professionals with additional training and a stricter code of ethics.