As long as he gives you the proper notice (usually 30 days, some places 60 days - check the laws where you live), he can terminate your lease and have you move out.
If you are not ready to buy a place yet, then look fro a rental that will take you on a month-to-month basis. A lease is nothing more than a contract, and both sides have a right to negotiate it (doesn't mean the other side has to accept it, though). So look around, and be upfront about your desire to buy.
Or, if you have family in the area that is willing to put you up for a couple months, put your stuff in storage until you buy a place and ready to move in.
You cannot force your LL to continue to rent to you after your lease expires. You have been given more notice to vacate than the law requires, so plan on being out by the date of your lease expiration.
It is not the LL's problem that your new place will not be ready before then.