I am looking at making an offer on a house with a crawl space.  It is on a very flat lot and has a problem with water standing around the foundation, and under the house.  It was built in the 1960's and apparently the moisture has caused the flooring to rot and has given way.  I am trying to think of a way to address the lack of drainage.  Don't want to repair the floor, just to have it rot again.  I can't imagine a french drain working because there is no lower point to run it to.  What about putting down a plastic water barrier under the house?   (Would a bank loan on it with this solution?) Any other possible solutions?  I need to get a handle on this so I can factor the cost into any bid on the place.  

A plastic barrier will do nothing to help the problem of standing water. You should consider a sump pump, which is a cheap but less than ideal solution. You can regrade yard around house to keep water away and waterproof the foundation wall. If it is relatively flat, then it shouldn't be too hard. If you do both, then you should be good with clean gutters. The yard may still be wet, but you can keep house dry. However, you should consider if there is extensive rot in the joists too. It can be quite expensive to replace both and the improvements above them. You'll probably find lots of rotten joists. So, I would budget a high contingency amount or just run (and avoid a potential money pit). A good real estate investor knows when to fold. Max

There are also subterranean storm water detention systems if the volume of water is greater than what a regrade and a few rain gardens will handle, but I agree with Max, this will only add to the cost, and if the structure is rotted out anyway, "money pit" sounds like a good name for it. Best of luck, Joseph

You could try to dig drain or french drain around the house leading water to small "pond" or water garden filled with gravel more than 8 ft away from house - it will attract water and move it away from foundation and may look even beautiful. Install dehumidifiers inside house running constantly. Sum pump will move away some water as well. May be just start with digging small (or big) pond (hire somebody with real equipment) and it may solve your problem

all good ideas. digging around the house and installing drain tiles would also be a good idea. run the drain tiles to a drain system a good distance from the house so the water travels thru the drain tiles and into the catch basin and away from the house. the key here is to get the water away from the house. you cannot stop water, but you can redirect it. these ideas are expensive, yes, and should be factored into the overall costs associated with the house. if the numbers don't crunch right, run the other way

Thanks a lot for all the great ideas.  I will inspect and see if the house can be saved, with a wide margin of safety for profit.

Before you try any DIY system consult with a drainage expert. Ask for a bid on doing the needed repairs and installing a good permanent solution. Usually you will not get charged for an estimate. Some companies do charge for estimates so I would first look for those that offer free estimates. Also you might consult a soil or structural engineer they typically will not come out without charging you but you will have a professionals view point of the problem and the costs involved. If this is too much for you then run away don't walk and avoid the money pit potential. Real estate investing is not just a matter of making money but of giving someone a decent home to live whether they are buying or renting so do your best to offer something of value and remember buyers are investors too and renters have rights.