Side self-employed business to be eligible for a solo 401(k)?

[K Luu]

Hi BP, I'm new to the forum, and have a question about converting a traditional 401(k) into a solo 401(k) with checkbook control to be able to invest in real estate, and what constitute as self-employment to qualify for a solo 401(k)?

Quick background: I have a regular W2 job w/ it's own 401(k) plan, but recently changed job and want to convert the 401(k) from the prior employer into a solo 401(k) to invest in real estate. I've contacted one of the solo 401(k) companies and have an idea of what's involved.

My understanding is, you need to be self-employed and make at least $500 or more a year in income to qualify for a solo 401(k), correct? Some people have a side job/consultant job that would qualify in additional to their regular W2 job... 

Since I'm just getting started, my "side" job has not been fully established yet, but I wish to tap into the prior 401(k) to do real estate deals. I do misc consultation on the side (for a kids robotics competition, for example in the past 2 years) and misc jobs, down to mowing the lawn, car maintenance for neighbor/friends, fixing things around the house, selling on Ebay, etc... that I collect "income" for, but they would add up to >$500. If I also do day-trading (stocks) in a personal account on the side, can I report my profits from day-trading as "income" to pad my side "jobs", since that would net >>$500/year? I plan to expand on the consultation gig eventually once I get settled. So is my self-employment "job(s)" legitimate if I have a paper trail showing receipts, etc of how the income was earned, and thus qualify to open a solo 401(k)?

Thanks in advance.