Most likely you will buy a property w/ an existing structure and need to tear it down. The price will vary according to the value of the surrounding properties. Entry level is 300K, but realistically, you will most likely spend a good deal more.
My husband and I have been building and renovating homes in Princeton (the boro and the township) since 2002. We have paid as little as $335,000(2002) to as much as $1,450,000(2006) for boro tear downs. We have yet to buy an empty lot as they are few and far between.
The location and the size of the lot will make a big difference in price. Don't forget to factor the cost of demolition into your budget (30k-50k)
very little about area. tear downs are most common. Depending on where in town could be as low as mid 300K to around 1M (this is for mostly twp though as University owns most land) In boro proper you will likely spend 2-3M.