I have a Home Equity loan question?

I own and house that is appraised at 106,000. I took a home equity loan out 2 years ago for home improvements. The balance is 28,000 left on it. My wife and I want to get another home equity loan and buy a smaller house to use as a rental. I am not sure how to you figure how much equity is left in the house. if someone could let me know then I would know about what price range of a house to look for. I realise that this equity loan would have to be financed with the new one. Just not sure how to figure equity on 106,000 house and owe on equity loan 28,000