I doubt: 建筑商能拿（贷）出很多钱建房.

80%+ of such developer/builders are dead.
They need you more than you need them. Of course there are Toll, Khov, Ryan, Pulty... now doing very well, but most mid-small size builders are not cash rich. Commercial loan for new constructions is still tight, although much better than 2 years ago.
I guess they need you use cash to buy the land. After than, some banks could finance 100% on site improvement, construction costs, etc. with LTV <67% (because land cash is in). Pay attention to, who is guaranteeing, what collaterals they require, etc.
Put is this way, if B and C can sleep together, why they need A?