I would normally say hire a locksmith o go and change the locks and hire a clean out crew to get their junk out of there. 

A kit costs about $12 and is a lot cheaper than a locksmith or purchasing new locks.

Do I need locksmith or call HUD for this?

She has given me permission to check it out but I'm not about to look like a burglar and she doesn't have the money to spend on changing the locks or getting a locksmith again.

They will be familiar with the local requirements, don't just hire a locksmith and cowboy it.In general you can secure the property but you cannot deny access so you will not want to change the locks on all the doors, leave one unchanged to provide access.

You might not need a locksmith/plumber/mason in the buying process, but I can assure you that you will down the road. - does real estate full time.

We understand construction, I for the last 8 years have operated a small locksmith business.

After closing I came to realize some of the keys don't work resulting in having to get a locksmith.

If nothing else get a locksmith to drill the lock and open it.

We would go so far as to facilitate a lock smith or maintenance person arriving with ownership to change locks if it came down to it.