Well written contract, general liability and E&O are requirements. I have done it without even when I know better and the reality is you can never predict when some ass will sue you. And even the best contract can't prevent a suit. And even the best lawyer can't guarantee you an outcome. At least with a properly formed LLC or other Corp struct and the proper insurance and documents you are in better shape.
Side gig you could setup a LLC run it properly even without E&O and within reason if you do get sued the worst case is a judgement against the LLC. You will still be protected and only direct assets of the LLC would be at risk. Bankrupt it, close it and move on. Not advocating this way but this is how a lot of home contractors operate.