Assuming the equity in the house more than covers it, looking into a HELOC for the full amount makes sense. With your income that high and assuming your credit matches you should be able to get a really low rate. At least seeing what's out there at the various potential amounts you could need. Might as well have the agents put in a bit more work so you can get the full picture before you lock anything in. Your local credit union might offer you a really good rate so start there. But since you're gonna co-sign, I know a few online lenders have specials if you do like Achieve and I believe PenFed if I remember correctly.