As with all things, tracking your Income AND Expenses are the key.
In my case, I plan to use rental income to finance my first few years of FI.
If I had 12 doors generating $300 in cash flow/mth ($3,600/mth), I would work to keep my spending below $3,600/mth, and use the cash flow to finance FI. While living off the cash flow, my investment accounts - 401K, IRA, Roth, HSA, and taxable accounts - can continue to grow UNTOUCHED. In fact, I plan to add doors until I have enough cash-flow to cover both expenses, AND have enough left over to add additional contributions to a solo-401K as owner of my "property management" company.
It was an eye-opener to me to realize that the 4% SWR discussed in the Trinity study is for the withdrawal rate in the FIRST YEAR of FI.
In the second year, one would withdraw the 4% SWR + the cost of inflation ~3% = 7%. Rinse, lather, repeat.
If you think about it... if you continue to withdraw the same amount, (4%) every year, while the cost of living goes UP by 3%, the retiree either spends the additional 3% to keep the same lifestyle, or experience a 3% shortfall in spending for the year.
By living off cash-flow, you can delay draw down of retirement investments, and allow them to continue to grow.