The question about how much a developer puts in is obviously related to his track record but 99% the banks ask for a personal guarantee anyway which is why many developers use the holding companies as a shield to their personal assets, sometimes even this fails in court.
On projects I've done, I always go for a subject to rezoning. The larger developers sometimes opt out of this due to their Council connections or confidence in the process.
The golden rule used to be 33% land acquisition, 33% construction/entitlement/33% profit. Economic times have changed it, now often what separates successful projects is land acquisition because construction costs are almost fixed. Another crucial factor is holding costs...on larger projects, if you don't option the property, you can be paying $20,000 month in holding costs while you wait 2 years for rezoning.
For me, 15-20% is yellow, proceed if your project is dialed in. 20-25% is green light for go. Anything above 30% is a special project...