Buying lot that isn't parceled yet

[Michael Retherford]

I am wanting to buy land that is advertised as 2 lots without any house. They have not parceled the land and it is currently parceled in with the sellers house. I have checked the country appraisal maps and it's indeed all one property still. 

If the seller is advertising that they only want to sell land, does that parcel cost fall on them to seperate it from their land with a house? What is the usual procedure for that?