If you already own the land free and clear, that's at least 25% of the cost.
We have gone through this math. Here's what we concluded:
1) building (hiring a small-scale builder) vs. buying new built home from developer (we tried to compare models as close as we could find):
- cost, building plus land purchase, was 90% of the developer-built (they do have to make their money, I don't blame them)
- building, you have a say in what model -- we wanted at least one or two bedrooms and a full bathroom on the ground floor of two-story, and no developer that we saw does that
- Developers have only three-four standard models and all you could change is the finishing, any other alterations start avalanche in cost
- Builder-grade is apparently the crappiest grade of materials you could get -- that's developer; building "yourself" you can at least control to a point the quality of materials used
- Building "yourself" is a hassle -- you have to work a lot with your builder, on every step, you have to keep track of plan approvals, etc.
- Building "yourself" you are not immediately tied in to an HOA -- those fees could be significant
- Building "yourself" you have to find a construction loan, which is not as easy as a normal house loan
(you can guess I'm prejudiced against developers, but it removes a lot of hassle from you)
2) Buying a "used" house and bringing it up to a decent condition, similar to a quality new-build:
- Cost outright -- buying "used" would be $100k-$150k less, but then replacing the bathrooms, roof, HVAC, septic, brickwork patch-up, leaky basement and mold fixing, etc, would be that same $100k
- (There are two types of basements -- ones that leak and ones that will leak)
- So, from our calculations, the cost is the same -- you just spread the $100k difference over time
- Have to find separate contractors for all the jobs -- hassle
- You can find a gem "used" house that was meticulously maintained and does not need all the replacements and upgrades, but it takes time and you have to jump on it right away.
That's what our experience was for a house without utilities, and having to find and buy land. Your situation is slightly different. Hope this was helpful.
We decided to go through "find land -- find builder -- construction loan" route, still in the process of it. If you want to know who our builder is, PM me.