Start your own business, get a small business 401k plan, pump as much money and assets of value into the company as you can, amortize those capital investments, buy services from your own company, give yourself a salary, do a company employment matching of 25% of your salary, pump remaining income of the business into your SB401k up until you hit the legal max (51k-403b).
This will give you the legal maximum of maximums for company contribution wihtout getting a partner involved.
This also allows you to take a large amount of tax breaks and credits in several areas, decrease your overal AGI, and thus lower your tax bracket, and take tax breaks over time, which all in all, give you massive advantages income, tax sheltered investments, and purchasing power wise.
Additionally, build your business credit. Allows you to borrow, and thus leverage potentially as well, your standalone business credit.
It also builds your business a history of income due to continual business (with yourself of course, and potentially others).
All legal, all legit, little paperwork, clean books, clean hands, happy pockets. I've done it for years.