Important to really analyze
DIY is half the cost
The good news is that you can build your own home for half the cost compared with having someone build you a custom home. The bad news is that construction materials are still pretty expensive, so you are going to need a big wad of cash.
Still probably need a loan
In an ideal world you would have saved up a bunch of cash and can use that, but if not then you are going to need a construction loan. Getting the money to buy the land will typically be different from getting the money to do the actual house construction. There are lots of resources on the web that will help you find a good loan, and brick and mortar banks can also be very helpful, so I will not dwell on getting loans on this web site. Getting a suitable loan is left as an exercise for the reader.
Plan house size to fit your budget
What is important is to figure out just how much money you will have available and to plan the size of house accordingly. Building a house is always more expensive than you initially think, so you also need to plan for a buffer margin. You really do have to be careful that you don't run out of money before the house is built enough to be signed off by the building inspector. Without building inspection sign off you will have a hard time selling the house, or getting refinancing on it. One way round the problem is to plan your house build in multiple phases so that you have a livable house after each phase and then your dream mansion after the final phase. That way you can stop after a particular phase if you run out of money or can get a home improvement loan on the phase one house to finance phase two. The downside with multiple phases is that you have to keep conforming to the latest building codes, but even so I decided to go for multiple phases with a different permit for each phase. I like the flexibility that multiple phases provides.