As my realtor business takes off I can hone in on investing to supplement my retirement. 

If I can't net cash flow $3k a year (a number I set for myself) prior to depreciation the deal doesn't make sense.In your case, you could house hack a 3-plex i.e. get in with a low amount say 5%, because you live there, (I don't see coverage of costs with a 2-plex if you live there, without supplementing with your own payments).I use Fannie Mae Matrix as "what I can do", https://www.fanniemae.com/content/eligibility_information/eligibility-matrix.pdfAnother example, I have also been eyeing vacation properties for my family.

The HELOC is treated like any other mortgage but if you have supplemental income that is supporting the property, your DTI should be fine so long as you are not over-leveraging beyond the point at which banks will lend to you.Also, I am a big fan of local banks because they are more personable and flexible. 

I much prefer being an investor with my license as a supplement. 

Do we just want to have a few properties to help supplement our retirement, do we want to have enough properties to replace my income and have this be my job or do we want to swing for the fences, grow a large portfolio and then sit on the beach somewhere.

You don't have to exactly replace the debt if you have cash from the outside to either provide the full amount or to supplement the down payment. 

The A/C is set low and is always running, and its always dark inside because the lighting was originally designed just to supplement all the light  the original double-glass doors let in.Not all service station minimarts sell equal amounts of convenience food.Invariably, the worst places are located in a food desert and run by independent operators.

The stock market is not the enemy, and a balance of safe investments is a great supplement to a real estate portfolio.And again following up on Alina, actually liquidating is the least preferable, as you will most likely be penalized as well as realize a taxable event.Disclaimer, I am not a licensed tax professional, nor am I an investment advisor

Should I rely on the rental income to help supplement the mortgage or should I be able to cover the mortgage based on my current Jobs income?

I would consider supplementing your income with wholesaling.. it’ll be good practice for running numbers and networking with local investors.