In my opinion you dont need a lot of capital, just a lot of people willing to buy through you, rather than the developer. Many investor groups have links to a secondary group or deals with lawyers on fee's etc.
I imagine somewhere along the line you need to provide the developer with a repuatable company name that you are attributed to, otherwise every Tom, Dick or Barry would be getting discounts off the developer. I buy through a group as its so much easier and they have a legal department who ensure the contracts are safe on the investors side. If you know nothing about contracts I would steer completely clear.... Instead pay someone a reasonable fee to do the donkey work for you.