Using builder's finance company to close the loan

[Venkat Varad]

I'm in the process of purchasing a new investment home from a known builder. Initially for prequalification they asked for lot of documentation, which I provided and approved. I was told that, it is part of their process to make sure the buyer is qualified. I understand that part, they want to have some surety.  That is fine.

Their finance guy is kind of forcing us to use their home finance rushing us to sign the papers, which we are refusing. I have my preferred lender who closes in time and better rates. I am in this field for more than 10 years, know well about home purchasing and done more than 20 purchase loans/refi's, but this new to me. Never been forced to use their lender. I don't want to pay their exorbitant fees and costs. 

Is that even legal? Anyone faced similar issue?. Any pointers to applicable laws are appreciated.