It is important to understand how the financing process works when building the property yourself. The process is slightly different.
There are 2 parts. There is the buying of the land and the subsequent building of the property. The purchase of the land is like any other purchase. You can receive up to 75% of the land value. When you are building the property yourself you are considered to be the Kablan ( developper), even though you are not building the property yourself and you have builders constructing it for you that you need to pay.
This is different from when you buy the property from a developper, where he organizes everything for you and you pay the whole amount at the end of the project. In this case you are acting as the developper and you need to pay all the different workman , and materials yourself. The bank will give you the money to pay you at the different stages of construction.
The mortgage is released at different stages of the construction process. The bank will send an appraiser to check the different stages and they will only release the funds as you complete the stages. The appraiser is also sent at the end of the construction to check that is has been completed, and sometime it is possible to borrow more money if the property is worth more than originally expected. The bank will want to see the contract and all the building permits for construction.