How to get extra into Roth?

[Pixel Rogue]

How can one get extra into Roth retirement funds? Yes, would consider gong to extremes to contribute extra.
• Employer sponsored plan does not support the requirements surrounding super/mega Roth contributions. 
• We have LLCs, primarily real estate rentals

---IDEAS---

• Create an LLC company to manage rentals, charging nominal monthly fee for management.
   Fee amount then converts rental income to active income, that in theory, can be used to fund a SEP or SD 401k
  May not be worth the effort given caps and % of full income... income is relatively small, so if limit capped at say 25% of net, not worth pursuing. 

• Considering a short-term air-n-b option to keep rental income active, however not clear on limits or gotchas - might be subject to same 25%.

• Having one of the current LLC/s contribution (on behalf of the company) to me, the employee, 401k ~ likely same 25% limit.


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What other ideas are people using to achieve same outcome?