If he is still there, you can't move in. You can't hire a locksmith. If he doesn't honor the date to vacate, you can go to a hotel and sue for the additional costs you incur due to the failure to vacate. Keep all evidence, get as much written evidence as possible, and take photographs. On closing date, tender all of the money to the title company, fund the loan, and sign all of the documents. If the seller fails to close, you then have a suit for additional damages and specific performance. Find a good local real estate lawyer to help you with this. Best of luck.
Actively practicing law in Texas. Inactive licenses in Arizona and Georgia. All answers are general in nature and no attorney/client relationship exists in this forum.
If under the terms of the agreement you were allowed to move in the seller cannot force you to sign an addendum undoing the agreement. If they refuse to provide you access you may have a claim for damages you sustain. For example, obtaining alternate lodging, storing your belongings and other like expenses.
You should try to resolve this issue before trying to move into the property. You cannot unilaterally change the locks, as you are not currently the titled owner. You may wish to retain counsel to make a demand upon the seller to honor the agreement. Best of luck.
This response is for general information only, and should not be construed as specific to the poster's situation. The poster should contact an attorney and meet for a consultation in order to be advised as to their options based upon all available information.
First off, agree with the other attorneys here and DO NOT HIRE A LOCKSMITH TO CHANGE LOCKS. That type of self-help will put you in a MUCH worse position. That said, your options depend, in large part, on the details of your sales contract and addendum. The Seller seems only to GAIN from the rental situation - so their refusal is suspect on its face. This irrational behavior could be indicia of some type of fraud and you should seek the assistance of a local transactional attorney as soon as possible.
It could be that a carefully crafted demand letter would be enough "push" to get them to behave - or, at a minimum, force the fraud to be revealed. In any event, the cost of this type of assistance would be well worth not having to continue with your family in limbo.