each spec home should be a current asset account named for the lot number or address, a work in progress account, wip

then you post all expenses to that account, a CC charge is entered and the wip account is the expense for that entry, same thing for cash or checks.  When there is a draw on the construction loan account open the loan register from the chart of accounts and make a new entry as an increase and use the wip account in the account block of the register

As an option you can also set up the construction loan account as a credit card type account, some find it much easier to use that way since you do not have to use the register and you just enter CC charges on the loan account when there is a draw - I prefer this method myself