will I have to forfeit my lease agreement with my current landlord if he sells his business to someone else?

What does your lease provide?  Unless the lease provides otherwise, it won't terminate upon sale of the busness.  The new owners of the business would have the same rights and obligations as the old.  If the lease allows the current landlord to kick you out (for example, if it provides that it can be terminated on one month's notice) then the new business owners can do so as well; if the lease prevents the old owner from evicting you, then it will prevent the new owners from doing so.  The above assumes that either the sale of the business is an equity sale (e.g. the sale of the stock of the corporation which runs the business) rather than an asset sale (e.g. the sale of the business' assets, like its real estate, trade name, supplier contracts, etc., not its equity) or, if it is an asset sale, that the new owners either assume the sublease or are aware of it when they buy the business.  If the new owners buy the assets without knowing about the sublease, they might have the right to kick you out, but you could then sue the previous owner for damages.