You will need two things for it to work very well on your 2N. 1) It will need the PTO driven hydraulic pump. 2) A sub frame mounting system. The three point on a Ford 2N will not take the force a backhoe puts on it.
I also assume you are meaning 5 foot not five inches??? The rated digging depth is with the boom almost straight down. One with only 5 foot digging depth would be pushed to dig 3 foot normally.
If it has those two things you should be able to buy in under $1500 on the high side. A five foot machine is small and not many want that little of a hoe. They are not selling like they used to because of the small track type hoes that can bought.
The three point back hoes beats a shovel but that is about it. They just do not have the force to really dig in hard conditions. Most of them have limited swing force too. You have a hard time using the swing to back fill with the smaller hoes. If your are on a steep slope side ways they may not be able to swing a full bucket up the hill.
Also look at how wide the bucket is. Real narrow buckets are a pain to use. The dirt/mud sticks in them and is hard to get out. So unless you have real sandy/fine dirt it gets frustrating to use a narrow bucket.