Your lowest interest-rate would be with the mortgage. You can get a mortgage because a mortgage is a loan for a real property – that means land with permanently attached structures. (You wouldn’t get a mortgage for the mobile home but you can get a mortgage for the land it sits on.) If you have at least a 20% down payment it will make the loan much easier to get.
You could also try to get an unsecured personal loan depending on how good your credit score is. But the interest rate would likely be 6 to 10% rather than 3 to 4%.