Start now or in 2024

It is better to start in January: otherwise, you will immediately lose your social security contributions!

Isn't this just €95.88 if I stay below €1,800?

Your social security contributions are calculated on your income anyway, so they will not exceed the minimum contribution if you make a loss. This is currently €95.88 quarterly. You can find detailed information about this on the websites of the social insurance funds (Acerta, Xerius, etc.).You may also be able to deduct the loss from your secondary occupation from your main occupation. The purchases of equipment are probably investments, which you will have to depreciate over several years. So I think it would be better to become self-employed in your secondary occupation this year.

If you decide to do this before 2024, make sure you register on 02/01/2024!

This will allow you to avoid provincial tax for 2024, as they calculate this for a start-up on 01/01/2024. From 02/01, you will not receive that invoice in 2024, but only in 2025.