First house, found foundation problem

[Sophie Sawyer]

Newbie to real estate: My offer got accepted but turned out there are foundation problems. The inspector estimated 8-12 piers for $3000ish. I asked three foundation companies to provide an estimate, their estimates are 10 piers, 12 piers and 8 piers respectively. However, the 8 pier guy recommended 20 piers to fix the whole house. My realtor recommended a 4th foundation contractor his coworker used before and this 4th guy's estimate turned out to be 23-35 piers to support the whole house. Their numbers vary so much that I'm now confused and scared. To make matter's worse, the 4th guy's estimate didn't come out until my option time just ended. Now I have paid $3500 earnest money and kind of stuck with this house. What can I do?