@Vladislava Kobeleva
Building costs are rising incredibly rapidly. I am building a few new homes including two 2 family houses in urban areas of NJ, and can tell you that it's very hard to just assign a price per foot in any times because of different design, complexity of the project, materials specifications, fire rating, sprinkler systems, conditions on the lot, ECT.
Here is a current example I am dealing with. In some of the dense infill builds (a house I am building in Newark), there is no where to store fill dirt after digging foundation, so you need to cart it off site, there's no room for a dumpster so all trash gets packed in the center of the house then live loaded periodically. The cost for the all permits alone for a 2 family was about 12k. Lumber has skyrocketed, and production time on vinyl windows is way way behind leading to longer lead times, good subs are busy so they either want more money or can't get to you for a long time.
In your case I know that many towns out there do not have city sewers or water so you need to install septic and well, lots of areas have bedrock base which is difficult to excavate for new footings and foundation, and the complexity of the plan (corners, large open floor plans, big windows, ECT) can dramatically impact pricing.
I would say between $200-$300 a foot to build right now (mid range quality product) Is probably not an unreasonable forecast, plus the cost to clear the lot of the existing building, permits, carrying cost, and closing costs on both the buy and sell side should also be accounted for.