Call around to local banks and ask about construction loans. For most construction loans, you will need to own the property, although shopping around may find a lender that will lend on the property as well. Once you find a lender with the right terms, fill out an application to get pre-qualified - this will let you know how much you can afford to spend to build. Most lenders require 20 to 25% equity in the house - meaning if the house you want to build will cost $200,000 to build, they will lend you say $150,000.
Under a construction loan, the bank will put the cash into an account that the builder/contractor will draw against to build the house. While the house is being built, you make no payments, but accrue interest. When the house is built, the amount lent (construction loan principal) and accrued interest will get rolled into a conventional mortgage.
The largest mortgage you will probably qualify for is $300,000 (three time total annual earnings) - figuring on a 20% deposit, you can probably use $75,000 of your $100,000 as a deposit on a $375,000 house, which means a $300,000 construction loan and leaving you money for closing costs.
Of course, these numbers are only tentative and will fluctuate based on interest rates, build time, your particular circumstances at time of build and the bank's policies.