Lol, I LOVE Tacyon's answer. I just wanted to put in my 2 cents worth from another standpoint. I doubt the one-time event would be a problem outside of a 1099 type transaction, however, I would wonder why NOT get your Part 107 soon? The industry is not going away, but it will become more regulated as it goes.
There are two basic areas of thought here. Yep, the "cowboy" method, and the sUAV service industry professional. If it's a one-off thing and you really aren't interested in doing more of this for $$$ other than as a hobby, then you might not see the need for Part 107. If you want to be a professional in the industry, you would definitely need to be reg/certified and keep up with the industry reqs.
I, personally, went with Part 107, and keeping up with the industry. I use my drones years to add around $8K to the services I already offer to a specific industry in Texas, as well as local farmers and ranchers. I also use my FLIR capable
Phantom 4 to help with SAR or defining hotspots for the local fire department, and do paid feral hog location services, wildlife migratory route logs, etc.
Everyone has an opinion. Mine is that I get to interface with some really awesome rescue operations, help people, and make some money to addd to my "UAV Addiction Fund", lol. Either way, who in their right mind would pass up some free food, lolol?!
Hve a great Day!