If your figures are right, then it shouldn't have any impact on your ability to sell the house. If you take out a HELOC for $55,000 and draw down the full amount, and the home is worth $125,000, then you would still have plenty of equity to cover your realtor commissions and other expenses associated with the sale. You would not be in a situation where you need your lender's permission for a short payoff in order to sell the home, so the HELOC shouldn't have any impact. Again, that's *if* your figures are correct.
A caveat for you: Equity lines are usually marketed as having little or no closing costs. But as we all know, there's no free lunch, right? If you read the fine print, you'll generally find that you're on the hook for some or all of those closing costs in the form of a penalty (perhaps called an "early closure fee") if you close your line of credit prematurely. For most homeowners, this is an insignificant risk. But if you're trying to sell your house soon, it could make the true cost of this interim financing quite high. Depending on your time horizon, you might be better off selling the house and using the proceeds from the sale to pay off your other debts, rather than taking out a HELOC.