I'm sitting on $100k from a recent house sale, but am reluctant to throw it into the market (face punch deserved for market timing).
As the LT stock market trend is upward, you stand to make more money investing it all at once. If you don't want to do that, you can always dollar-cost average your way into the market.
I was thinking - I have my primary house mortgaged (3.75%), so maybe I could put that $100k into my mortgage and then obtain a 10-yr draw HELOC ($50 closing costs and probably the same ~3.75% interest rate). This gives me a 3.75% "return" annually (from the reduction in mortgage interest) until I withdraw the funds to invest once the market corrects 10% or more.
Using the $100k to pay down your mortgage assures you a 3.75% return on that investment.
What if you pay down your mortgage and the bank refuses the HELOC, or approves it only for a smaller amount? It would serve you to know the target bank's LTV limits.
Alternatively, invest the money in the market and apply for a HELOC anyway. Use the $100k balance of your investment as an input into your bank's credit decision on the HELOC.
You may be able to obtain a 3.75% variable rate on your HELOC if you occupy the house serving as collateral; many banks are offering Prime - 0.5% or Prime - 0.75%. TDBank and some credit unions come to mind.