So confused about retirement accounts - please help

[Road42]

I don't know why this is something I can't quite wrap my head all the way around, but hopefully many of you out there are much smarter about this than me!

Ok so:

- DH works and gets a W2, and with that job he puts $18k into a 401k every year (and gets an employer match for some of that).
- DH also just started a solo business on the side, and has a SEP IRA for that, with whatever TurboTax claimed was the max possible to put into that account for last year.
- I work freelance (and so have a solo business) and put the max possible every year into a solo-401k (though I don't tend to make enough to put all $18k in there).

Questions:

1. Can DH open a solo-401k if he already has a normal 401k from his regular job? If so, is the max total he can deposit in these accounts $18k, or is it $36k?

2. Is the max for a solo-401k actually $18k?

3. Should/can we also have Roth or traditional IRAs on top of all of this? According to the internet, our earned income is too high for either of these accounts. But we could have a backdoor Roth, I guess? I read the backdoor Roth sticky post on one of the forums and didn't get the purpose of that mechanism if you aren't planning to withdraw money from retirement savings in 5 years.

4. Am I missing some big glaring thing (probably)?

Thanks for any insight!

[boarder42]

1. no
2. Under the 2017 Solo 401(k) contribution rules, a plan participant under the age of 50 can make a maximum employee deferral contribution in the amount of $18,000. That amount can be made in pre-tax or after-tax (Roth). On the profit sharing side, the business can make a 25% (20% in the case of a sole proprietorship or single member LLC) profit sharing contribution up to a combined maximum, including the employee deferral, of $54,000.

3. yes but backdoor roth is blocked for your H by the SEP IRA
4. HSA if possible goes way infront of everything except company match.