I want to make a tree house?

I have a fort on the ground and bugs get in it and it pisses me off. I want to make a tree house in the air about 6'-10' off the ground and I want it cheap. Im looking for a 2 tree tree-house and i don't know how i should connect the 2x6 to the tree. do i bolt it? drill a hole through the tree and put a rod connecting the wood to it? use screws? nails? Please be specific and maybe direct me to a link to where i can see pictures or a video of this. (I looked on youtube and i couldn't find anything.) Thank you! -Brandon