If you get paid by cash then the IRS will most likely not find out. But if you're paid by check or direct deposit from your employer or self employment income then the IRS may not notice for years but eventually will catch up to you.
Although rare a person not filing taxes can be sentenced to prison for 5 years and have their home, bank accounts and anything else seized to pay the taxes.
It's best to just file the taxes. You can't go to jail for not being able to pay but you can go to jail for not filing taxes and they see that as committing fraud to the IRS.