I think you can't avoid tax unless you change residence to another country because
your tax authority may request you to present them your sublet contract!
Then what?
Nothing. There is no need for either a written contract or an invoice between a private person and a non VAT subject partner. It doesn't matter if the other party is a company or a private person, until he/she/it is not subject to VAT.
You mentioned you have to rent space from legal entity A for 1000 / year. right?
Then you let this space to legal entity B for 90K / year .
What if tax authority in your country ask you to show also the contract that you have with legal entity B?
The non-written 'verbal' agreement is sufficient and legal in the above described cases. So you can legally only be asked to 'declare' the source of income.
In your case who will be the legal entity B in the contract
that will pay you 90K on your bank account?
Can you explain more in details please?
The payment arriving to your BTC address at your chosen bitcoin exchange is your income that you declare to have received as rent. The 90k to your bank account arrives from the crypto exchange you have chosen to exchange the crypto to eur.
For common "small" people is difficult to escape the parasitic systems
that are feeding on the working class and which you may know are designed
for the rich to become richer.
Only the rich have totally legal means to "lower" their taxes legally.
I agree. That is why I came up with this. To help the little guy (myself included).