Following Gary's post below is it possible to start off a SEP plan with 0 or 1 year eligibility and then amend it to 3 years later.
How about the same idea with SIMPLE IRA plans ? Can you amend from immediate eligibility to the 2 year/$5,000 requirement ?

There is no guidance on point that specifically addresses rolling eligibility in the case of a SEP or SIMPLE. Depending on the facts and circumstances the IRS could easily demonstrate (using qualified plan rules) that the plan is discriminatory. THAT BEING SAID, the IRS has allowed plan provisions that allow for current employees to participate in a SEP and future employees to satisfy service requirements. But that is not the same as rolling eligibility.

I'd be careful. Consider a PLR?