I'm a sole proprietor and my objective is to contribute as much as possible to my retirement savings. As my income fluctuates annually, one year the $6000 max of the SIMPLE would do, but another year my income would exceed $46K and a SEP would work better.
Three questions:
1. Can I have both a SIMPLE and SEP IRA and depending on my income that year contribute to one of them?
2. Are there minimum annual contribution requirements for SIMPLE or SEP-IRA?
3. To throw in another IRA: can you have both a Roth-IRA and SIMPLE/SEP?
Thanks for your help!

1. Arguably the arrangement could fly under IRC 408(p)(2)(D). [I MAY ALSO LIKE TO THINK ABOUT THIS SOME MORE; PERHAPS OTHERS WILL RESPOND TOO] All rules, notices, and so on for both plan would have to be followed / made. There cd be several problems if non-owner employee's were involved.

2. All elections for the SIMPLE wd have to be in place by December 31. No minimums in a SEP, can be avoided in a SIMPLE.

3. Yes.