@Spacefruit is quite right but with the addition of 'allow twice as long as you think it might take'.
There are many matters to consider:
do you already own the land?
what is the condition of the land?
do you have the correct permissions to build?
what type of house do you want to build?
all of the above could affect the time and cost of your build.
find someone to design and cost you a house that you want and don't change the design after it goes to site or this will cost you both time and money.
once you have a site and a design, get a site survey done (topo and geotech) before you start anything else - most unlooked for overspends are in the ground.
find a contractor who is both competent and experienced at building the house you want - in the place you want to build it.
make sure you have a proper contract that you can rely upon.
ideally have a professional administer the delivery of the contract.
if you want the house to be 'just so' get a full set of drawings done (with details and materials) and have a contractor price it.
if you're happy with a 'nice house' with no particularly special items, you can use a more 'design and build' approach, (effectively using planning drawings with indicative details and materials) this will likely be less expensive.
for both options you can get a fixed price and have the contractor take the risk (excepting that you can never- ever- be sure of what is in the ground).
Ideally get three prices but if there aren't that many competent contractors available get your professionals to sense check the prices you do get.
You don't have to go for the most expensive contractor but don't take the cheapest price because its the cheapest.
Finally, if there are client decisions to be made, make them quickly and decisively - this should help keep you on track for both budget and programme.
hope that helps (and good luck!)