I’d paint the center island to break up all the wood.

@Brent Thompson - the potentially difficult part is how much concrete they have to break up to reach a sewer line and if any demo then framing needs to be done.

@Maugno Mora You can always abandoned the current main water line in place and just run a new line so that you don't have to break up the cement driveway.A Ditchwitch can be rented from Home Depot tool rental for not too much money.

I would also have an agreement among the “tenants in common” or as an LLC  so when the circumstances change, someone dies, or gets sick and wants to sell, divorce, etc you agree on how to handle the break up.- basically a prenuptial. 

How much for the breakup fee...etc.Any advice is appreciated!

I would like to marry her but dont know if I'd bet my house we'd stay together.I know this sounds cold and calculating, but when you hear stuff like "if we break up I wont get anything".

We made an offer and the sellers accepted our offer of 335K but the banks will not come to an agreement on how to break up the amount we are offering to cover their debts.I understand that the first bank has collection rights and the second bank only can recoup what is left.

lol So nice to break up winter a little bit!!

@Andrew Fidler  also check to see if there is a "Dominant" and "Subordinate" description to the easement between the parcels or any "exclusive or nonexclusive" use as future control or access can potentially be lost during a sale and break up of parcels. 

You'd need to have clear answers up-front for unplanned costs and who pays them, who inherits property if one of you dies, what happens to the investment if you break up, etc.