can you explain what a land contract is suppose to be ?

I have been had by a man that sold me a section of land (9 3/4 acres) with a old doublewide trailer on it. He said he would finance it @ $750.00 a month with $40,000.00 down on the loan. Stupid me did sign this agreement, now I find out through the grapevine, he went and got a 2nd mortgage on the property and apparently has gotten behind in his payments.. I had a stroke and heartattack over this , worrying about this. He now has threatened to foreclose unless I come up with almost $3200.00 which considt of 1 missed payment of $750.00 and the rest is $100.00 a month that I was to pay on the taxes and Insurances on property. All this and yet he has not given me any figures of how much the mortgages are nor the taxes or insurance on anything. I can't even get the credit on taxes in my county cause I don't have a deed of trust. Can anyone advise and help me I offered him $750.00 payment today and he refused the payment. The contract he drew up stated 2 missed consective paymenst he cvould foreclose on the thrid month, which is not here yet, and he is refusing payment.. HELP Please somebody out there ???