Through passive income, I hope to gradually supplement my salary and replace it completely within 5-8 years.  

Gradually, as I've acquired capital and relationships with private lenders, I've transitioned my real estate activities from being a commissioned agent to being the principal in 90% of the transactions I do. 

The landlords duty of care is gradually encompassing not just tenant but the public at large.

In the case of the HELOC, you use it like a checking account so all of your surplus funds pay the balance down gradually and again, you're technically making extra principal payments every month, but since you aren't really missing the money it's like your mortgage is automatically being paid down faster.

A rental with great cash flow will also help but its a pay off gradually rather than a quick pay off/down.Cash out refinance is a better way to get the funds usually because the cash out refinance offers a lower payment. 

I know if we stick on this path of gradually building our portfolios, we will definetly accomplish these goals of being financially free!

Gradually building up monthly cash flow to eventually match, and surpass my regular day to day career. 

We closed up shop with the service business for good this past summer after gradually cutting down on hours put into it and I've been a full time Realtor for about 6 months now. 

If you do let them tie up the property you should have a gradual pain point.For example 90 days and 50,000 earnest money of which thereafter 20,000 becomes non-refundable.

Once I have established some funds, I can then gradually start looking into investments that offer the benefits of cash flow.