I picked up a portfolio of homes the previous owner had for 15+ years so I'm dealing with what seems to be a lot of deferred maintenance.

Take Roth for example: it is not just tax advantageous, or tax-deferred, it is tax-free!

This would essentially defer capital gains until you either 1) sell the new deal or 2) die and the IRS cleans the slate.

I defer back to what I laid out.

If it’s addressed, defer to that.

if you haven't already, do a Capital Expense/Deferred Maintenance analysis of all six properties. 

If you have a worn out property with a lot of deferred maintenance in a lower end area that does not typically have the best tenants, then it may be worth it, because you will have more calls, more tenant issues, harder time leasing, more turnover work, etc.

Retirement account taxes will be deferred for another 20+ years for year, real estate its depreciated but only deferred if you do a 1031 at sale. 

If there is no deferred maintenance to start with then you are just budgeting for repairs and dealing with them as they come up.

There's always going to be a limit on what you can do on your own if you want to grow your portfolio.  2nd idea-If your goal is to grow the portfolio in the short term and your unable to use a 1031 to defer capital gains I recommend you discuss with @Aaron Hickey.