Whether such a thing is reasonably safe (aka, "hedged") depends on whether your income outside of this proposal is:
1) substantially higher than your expenses outside this proposal, and
2) well insulated from external factors that could damage your ability to get the presumed 80k profit.
In other words, investing in the financial markets is not a real hedge for a remodel-and-sell home loan, but job income might be. What's your savings rate?
If my credit score was 690, my cash reserves would be low. In that case, I'd use a money market fund to store the loan cash while doing the project, if I were going to do the project. Heck, my score's 100 pts higher and I don't have big cash reserves.
Good luck though. My block is full of flips. I had a flip-oriented agent reviewing my house yesterday. Planning to hold in unstylish condition, though, it looks like. At least until I have a stronger income to hedge any expensive upgrade projects!
PS. Re Wealthfront per se, my guess is that it's not very valuable except in specialized situations that involve high taxable income. Vanguard is probably better for most purposes. One of their strengths is relatively efficient, reliable money market funds that would be good for stashing flip cash. Though having flip cash at all is only wise if you are truly likely to get substantial flip profits. Even then, it's wise to have a backup plan (a "hedge"...not Wealthfront) to cover deals that go wrong.