You should consider having the developer produce a line item development plan he/she is intending to pursue during the 2 year option period. The plan should show the sequential steps the developer is planning to take along with milestones they intend to reach. 2 years is a long time and may be required if actions such as annexation, zoning, site/project planning, permits and financing are involved.
If the developer knows what they are doing, they should have no problem creating and showing you their plan. If they can't or don't want to comply, pass on them UNLESS they are willing to pay earnest money which goes to you. If they don't want to pay earnest money, pass on them. Earnest money can and should increase as milestones are met since the developer's risk is decreasing at the same time.
Sep 23, 2012