Cash out refi or HELOC for new purchase?

[Robin A Jackson]

I realized today that I need some more savvy friends for pinging scenarios off of! I live in Portland, OR. I'm wondering if you'd be willing to give me your two cents on this. I'm going to include specific numbers. And maybe this will be helpful for other who face a similar choice! 

GOAL: I want to purchase another income producing property in about 6-14 months from now (depends on market and my energy).

I don't have a downpayment. 

I am refinancing one of my rentals and was planning on using a cash out refi for the downpayment on the new house (as I have done twice already to buy two other houses - both great choices!). 

Then I thought maybe I should leave the equity in and take out a HELOC instead later. Reason being that I might not touch the $75k cash out for up to a year and It's going to cost me $337/month extra so why pay for that? Why not wait and only take it out once I'm ready.

If I do a HELOC they will loan up to 80% w no closing costs. So up to 116k (based on my appraised value of 500k). 

If I cash out now w loan at 3.5%: 
75k cash out (337/month) 
+ $25k HELOC later if I want to go up to 80% (170/month) 

Of if I wait and do a HELOC later for 116k It'll be about $800/month for a 20 year payback at 4.875% 

My concerns with the HELOC are that the rate is variable. Though I can lock it in (at a potentially higher rate 6% later) And also I don't know if their appraisal will come in the same. Some unknowns there. Or if my DTI will work by the time I apply.

But if I go w a HELOC that also means I can do a non-cash out refi on my rental and that means lower rate and monthly payment of 1600/mo forever at this great rate, so I'll be saving that to offset the HELOC payment.

Lots of variables and "don't know the future" in this one! 

If I do the cash out refi I may  end up paying each month for a loan I'm not using and have a high payment for the life of the loan (and losing the cashflow) but it seems sure and safer. 
If I do the HELOC, I might end up paying more later on, however I'll save on the rental payment being lower and have more flexibility .

Anything I'm not aware of or perspective you see which might help? I'd be grateful! 

I am in the loan process already (appraisal just went through) so I need to decide quickly what I'm doing.  

THANK YOU! 

Robin