An equity loan requires that the home has equity, so based on another question you asked, if you are using a VA loan, you won't have any right away. How soon it comes depends on the economy, the home improvements you might make without it, and several outside factors.
When you do have some, or if you put some money down for the purchase, lenders may limit your loan to some percentage of value less than the future current value. For example they may say, HELOC to 90%. If you put down 10% and the home goes up 5% you'll be able to draw some, but not too much.