@Gary Fare:
Yes, you need to check the Due On Sale clause. People will tell you all the time: "Oh, they don't care, as long as you're paying the Mortgage." I prefer to take a more cautious approach to the question:
1) Have you consulted a lawyer? You SHOULD, if for no other reason than that most people who make the move you're making are looking for a reduction in (some) liability in some way, and the fact that you mention "fees and some other factors." Having the entire chat with the attorney will be exponentially more beneficial to your strategies than throwing a potential legal quagmire like this onto a social media site. (An intelligent, helpful, and precisely-targeted social media site, but a social media site, all the same.)
2) Have you approached your Lender to ask the question of whether they'll allow this change? Depending on your reps & warranties, your credit profile and your reasons for the move, they MAY either let you or will simply have good advice for you. Better still, if it's a small bank or credit union as opposed to "Monster National Mortgage Corporation."