Can you buy a real estate with bad credit (less than 600)?

Probably but I would research how to build your credit and also save up down payment.there are several really good podcast out there on buying land.The land podcast,the american land man,rec land realty podcast are just a few
Contract for deed with a big down payment. I don't like it, but if that's your only option and you want it badly enough it can be done with the right seller. Just know you've got far less protections because you have no title, you've just got a contract to get the title if you complete the contract.
IMO ,the down payment is the key. Put down enough,say 20% , most banks will talk to you. Go with a bank near the property.