Because you still want to allow employee contributions despite not having more than 100 employees who earned $5,000 or more (each) last year, you can consider a SIMPLE IRA. A SIMPLE IRA allows employee deferrals up to the lesser of 100% of their salary or $15,500 ($19,000 if age 50 or older), in addition to employee contributions.

Because you don’t want to allow employee contributions, you can consider a SEP IRA, which allows for employer contributions only.

As you noted that you’re willing and able to make regular contributions to employees’ accounts, you may want to consider a SIMPLE IRA, which requires an employer to either make non-elective contributions of 2% of an employee’s salary (subject to caps), or to match employee deferrals up to 3% of such employee’s salary (or 1% in 2 of the prior 5 years).

As you noted that you’re not willing and/or able to make regular contributions to employees’ accounts, you may want to consider an SEP IRA, which does not require an employer to make any minimum annual contributions. However, any contributions must be made equally to eligible employees.

With seasonal, part-time and/or short-term employees, you may consider a SEP IRA, which must be offered to only those employees who are age 21 or older, have worked for you in 3 of the last 5 years, and earn at least $750 from your business this year.

With full-time employees rather than seasonal, part-time and/or short-term employees, you may consider a SIMPLE IRA, which must be offered to only those employees who have compensation of at least $5,000 in either of the prior 2 years, and are expected to earn at least $5,000 from your business this year.

When withdrawals might be needed within the first two years of participation in the plan, it can be a good idea to consider a SEP IRA, because withdrawals within the first 2 years from a SIMPLE IRA are subject to an early withdrawal penalty of 25% (instead of 10% for a SEP IRA) when taken before age 59.5 (unless an exception applies).

Note that neither a SEP IRA nor a SIMPLE IRA plan allows loans. Contributions are 100% vested, and do not affect your contribution limit for Roth or traditional IRAs (but may affect deductibility of the latter)