I'd keep in mind that even though someone may find an activity profitable, it's often largely affected by the local laws and tax policies.

For example are a myriad of 10s-100s of bucks/month I could theoretically make that have demand and in many countries someone might do, but here it's

1) required to have a company

2) static taxes are several thousand/year

3) dealing with requisite liabilities and insurance lifts the monthly fees to some hundreds/month

So check those first before diving deep

I rent out tables for local ComicCons.

Good money in it, but a lot of the people who rent your tables won't keep them clean.

I somehow ended up on the government's poor people list despite being nowhere near poor, from my rural hometown, and I get enough money for a handful of AI subscriptions (to give you an idea) through the direct benefits program. I also get "for the family" notebooks and bags at the start of the school year, a phone every few years, a mixer-grinder now and then, sweets once a year, and more similar, all beautifully adorned with our chief ministers face. In practice I give the coupons and gifts away to one of the others in that rural area, and only keep for myself the box of sweets if I happen to be there - I live primarily in the city.

The local politicos know this mistake but weren't able to get anyone to fix it and remove me from the list. By now, they automatically know not to deliver the goodies to our address.

But as of the last couple of years, the money automatically shows up in my bank account, it's been digitized. So yeah it's an "income source" of around 13k INR a month. And I get credits back in the bank account as well for the cooking gas we consume, which is small since we don't live there much.

When I visit that bank next, I hope to get the whole damn thing cancelled. Hopefully the digitisation also means more quickly being able to cancel it.

I'm playing monsters in low-budget horror movies.

It’s fun to watch them with friends and family from time to time to laugh about the horrible acting.

For small and occasional activities it may be worth asking a tax professional how the local laws treat hobby income. In the past it has simplified my declaration of tax activity by avoiding business red tape for that class of income and I could declare expenses against it at small scale. It does have to be occasional or unserious enough to be classed as a hobby.