If I worked for my dad last year helping him paint houses and he paid me cash once a month what do I need to file taxes or how do I file for that year because he recently passed away and that was my only income for that year
You would be considered self employed so you report income on Sch C.
Yes, you are self-employed.
To enter your self-employment income click the following:
In the expense section, if you drove to different job sites, you may be able to take mileage or vehicle expense deduction.
This income will be reported on Schedule C which is part of your overall tax return. This also means you will be subject to SE Tax. If you did not pay SE Taxes in 2023, and if you took over his business, it may be a good idea to make quarterly estimated payments to cover your SE taxes of 15.3% and avoid penalties.