Income target of £300 per month from online freelancing - realistic or not?

Hi everyone.

I've been looking at ways to increase my income and I noticed on some threads that people have used companies like Appen, Upwork etc.

Some posters have indicated that as little as 30 minutes a day can pay £300 a month. However, from some Google searches it seems the roles are difficult to get, and entry-level rates appear lower than that.

I'm looking for some advice from anyone here who uses these sites, and any extra
info on how it all works, pros and cons, how much time I'd have to spend initially to hit the £300 target and then how long it's take to build the skills/experience to hit that amount in 30 mins a day.

As extra background, I work full time in the investment management industry so have a reasonable grasp of data analysis, regulation, and Excel but I've not got any real experience in coding, app development etc.

Thanks!