We have a good amount of equity in our home and currently have a $140k HELOC on it with a local bank.

Previously, we were able to obtain a 10 cap without undue risk (about 5 years ago); the. 3 or 4 years ago we were able to purchase at 7-8 cap and “juice” returns by borrowing 50% at 4% fixed 20 year financing.  

Depending on the amount of equity you have along with the cash flow that is existing right now, perhaps looking to do a cash out refi to capture some of that equity, keep your property and tenants in place?

My ideal plan (obviously with a little tweaking along the way) is to start fixing and flipping homes in my spare time, as I still work a full time job.

She invests in Fix and Flips.

I have one rental close by, rent amounts are crazy. 

Some didn't even add the late fee to the current amount due but to the next month. 

What documents would you require before you contributed funds in any amount?

Since home prices here have gone up, most of the investors I work with are just doing fix-and-flips because they have a higher ROI.

Look at your monthly payment (PITI = Principal,Interest, Taxes, Insurance) + HOA + (other maintenance fees if any) and if this amount is less than what you charge for rent (whether its Long, Mid, or Short Term rentals) and you are happy with the positive cash flow, then yes.Or maybe you're breaking even with the condo but you have  knowledge that the condo will explode in value due to some business/attraction/law/policy that will prop-up the sales price in the near future, then yes.Really, it boils down to what your goals are for this first investment.