My wife and I are interested in purchasing a piece of land for future construction of a nice home. We currently have a contract on this land. It is a foreclosure, bank owned and no surveys or anything are available.
The parcel is approx 6 acres, it contains part of a lake, there are some wetlands and possible some flooding risks.
Our contract now allows that we have 30 days for a "feasibilty study" to determine if the property fits our needs.
What all do I need to get done besides a survey (what kind of survey?) to make sure we can build in the future our dream home on this land as we hope for?

You should contact an engineer whose office can obtain the proper survey. Then that engineer can review the survey, review the zoning requirements, wetland requirements, flood zones, etc. They should then be able to prepare a plan that shows a footprint of where you can put a structure.

Wetlands can be a real issue, government can stop you from any use at all that would or could effect it. Flood zones could stop or require speical design in building permits.

And of course you are still liable for any future wetland or flood plain building restrictions until you actually build.

I would review though all requirements and restrictions on this property.

Often times you can find smaller to medium size builders that have all systems in place as far as engineers and they have the "team" in place to be able to get you the answers that you need. Find a builder that you like and there is a chance that if you negotiate correctly you could have them apply the money you pay them upfront for the study to your purchase when you use them assuming that the study pans out. If it does not work out, they would keep the money as payment for work done. Please make sure to remain within all deadlines and do not cut any corners as it could cost you much money in the future. I have seen it happen before.