I was wondering if I take my buy sell agreement from the original purchase of my home am I able to use it as a template for a new buy sell agreement, just customize it to my current needs, and have it notarized. Is that legal or do I have to obtain a real estate lawyer?

You could do that if you like, BUT you need to be sure that both buyer and seller are legally protected in the purchase agreement. Would this be for the same property or different property? Are you not going to be using an attorney for the sale? Are you going to be using a title company? Sometimes it is very tempting to leave out those expensive professional people, but in the long run it pays to include them as most good business is done with professionals involved. I would actually shy away from a "do it myself" type of property sale.

It would be for the same property and its 3 years old. And we would be dealing with mortgage company.

While ( legal disclaimer) always best to use an attorney and get a new one made, esp if their may have been changes in the laws after time.

** I have used the same or similar ones, I at times download a new online one and see if there is issues that appear to need to be addressed.

Please not this notory thing is merely proof of who signs, does not make it legal or not, just a witness as to who is singing