Does a realtor have to diclose to you if he knows there is a large surgical center going in across the street from your new home and they are going to do work on the road and assess you $1800.00 9 months after you buy it and he knew this before your purchase

If the realtor actually knows.

No, it would all depend on his morals and how greedy he is for the sale. Why, did this happen to you?

If you can prove the Realtor was aware of the assessment than you may have grounds for a suit. Knowing that a center was going in across the street isn't enough.

Was the lot empty or abandoned when you looked at the house?

No, the assessment , since it is a tax, should have been disclosed but the seller is the one that is suppose to disclose things to you. I will assume you did not use a buyers agent, but was merely talking to the selling agent