Can you afford a custom build? Most builders use a lot of spic labor and the cheapest supplies and subcontractors. Know what you're paying for.

I work for a subcontractor and the materials are shit quality. Better catch every deficiency in the first year. After that you're paying out of pocket.

I haven’t built a house for myself, but I’ve done it for other people over 10 times. A big thing you got to think about depending on which state you are in is impact fees for new homes. I know around here even if you already have a house on the property and you want to knock it down and rebuild it, if you don’t use the same footprint it’s about a $30,000 impact fee. It’s supposed to cover the cost of impacts on the roads and school system.

You also have to think about how far away the power lines are to where you wanna build. Here it’s about $50 a foot for them to run line. So if you want to build your house 1000 feet from the road, you’re talking about $50,000 just for the electric company to bring lines to the house. That does not include bringing them inside the home. An Electrician still has to do that

Obviously water and sewage are another factor. Septic systems can cost about 10 grand to install, and it’s going to be a big cost getting water to the house or hooking up a sewage line. Ideally you find a plot of land where all the utilities are accessible.

There is also the grading issue. If any of the Land runs at an angle back toward the house, it will all need to be graded away from the house so that you do not have water issues. Depending on the severity of the grade, one man with a skid loader or excavator can take care of this, but this is also not cheap a lot of the time.

One more thing to consider is deed restrictions. Deed restrictions aren’t just about construction. They may allow you to build a house and live on it, but then they won’t allow you to have any kind of RV or trailer on the property. This is very common in rural areas. A farmer will sell the land but will try to keep it from looking very trashy. So if you are planning on living in a trailer while you build the house this could get you fined. Many regulations prohibit chickens or livestock. It’s very important to understand the contract and what you are permitted to do with the property

I worked commercial construction for fifteen years and have built many homes. On the consumer side I've had one built for me, but it was a custom post-and-beam structure that was pretty damned expensive per square foot. Then again, we encorporated geothermal heating into it, which increased the up front costs. My wife and I are looking into building our next home instead of buying. Check with the BBB in your area of interest for information about reliable builders.

Edit: there are a number of large builders that offer pre-designed homes that can be built on your property. Toll Brothers and D.R. Horton come to mind.

Don’t sell your old house. Take equity out for your down payment, get something smaller than what you really want, and make money off renting out your old one. It’ll be passive income for the rest of your life with minimal work on your part. It will be an asset that grows in value.

Define "build a house" ... that means many different things.

For most people (95%), "build a house" involves hiring a builder who has an architect and subcontractors on staff. That's easy.

For some people, that means hiring their own architect and contractors.

For a few others, that means doing some / part / all of the work themselves. This is usually limited to the Amish and farmer type who know how to run a cement mixer and know how to do framing.

A few years ago I bought 40 acres in the middle of nowhere. I built an agricultural steel frame building on it. It is quite nice on the inside, but I made damn sure that the land was zoned agricultural, and that I was able to build ag buildings on it. That being said, I did not go with a traditional stick frame because the cost would have been ridiculous, and I have the ultimate open floor plan. I have done much of the work myself, and have managed contractors to drill the well, run power from the pole, concrete, and erection. I ran the circuits inside, insulated, plumbed, drywalled, hvac, etc... If I would have built a house, the taxes would have gone up considerably since the state taxes houses separate from ag land.
I wouldn't do it again, as I have the land and location I want. If I had never done it, I would do it again.
Pitfalls- The first is time vs. money. If you have the time, you dont have the money. If you have the money, and you pay others to do it, you MUST manage the site. Quality, time schedule, etc... The contractors must have a clear understanding as to what has to be done. Good contractors are not cheap.
2- Environment- is there drinkable water? Is there water in general? What is the soil like? Is the climate ideal for you? I looked into all kinds of places before I bought. I learned that in the gulf of mexico PVC and wood can rust. I learned that the eastern plains of Colorado has shit for soil. I learned Arizona is too hot, and most of the south is mosquito infested. Minnesota has shitty politics, etc... 3- You must do your own due diligence. From the land to the building, if you want it done right you will invest the time to know what you need and what you need to do. Contractors can cut corners, not run things to code, use shitty material, hide gaps, etc... It is your duty to be on top of all of them, and to take responsibility for your actions or inactions.

look at zoning regulations. They are very strict just about everywhere. if you want anything that isn't a 1400+ square ft, hand built lumber contraption with a 2+ car garage and 4+ bedrooms with closets you are out of luck. If that's exactly what you want fine, but otherwise it can be difficult to 'break free' from the cookie cutter mold they are trying to force everyone. there are a ton of construction techniques and styles that are amazing but in most cases they are 'technically' allowed but you have to get a debbie downer bureaucrat Karen to give you permission.