There are three disadvantages of renting. The three main disadvantages are not owning the place, having a lawn lord and losing money.
The continental army were on their homefront so they had more of a will to fight. It is easier to fight a defensive war rather than fighting an offensive war where you are on someone elses home court. The continental army also had an advantage because the british had to ship supplies from over seas while the continental army had their supplies right from their home. I am pretty sure the British had a powerful Navy.