It seems to me that it would be difficult to get a loan without having title to the property you are building on because the bank's lien would not attach to the ground, only to the building. The owner's of the land could require that the building be removed. Although your parents own the land now, having it left to 3 siblings - yourself included - when they die, does not solve this problem. The only way that a lender would likely feel comfortable with this transaction is if your parents gave you an interest in the property now. They will probably need to figure that out as to how to address that regarding the future interests they will grant your siblings.
This answer does not constitute legal advice and does not and is not intended to create an attorney-client relationship. The law may vary depending on the state in which you reside. It is intended only to give some direction in which to seek assistance.
There are several different ways of working this type of transaction as long as your parents are willing to be a part of it. The property could be placed in a trust and pre-divided for your other siblings. When you state that "me building" I assume you are having someone build it who is licensed or that you are licensed. Naturally, credit, down-payment, land value, and builder credentials will all come into play. Unfortunately, you will need an attorney who can do all of these things. Good luck!