Yes, one can definitely file ones own patent. One can also build ones own mansion. Are you interested in building your own mansion? Have you practiced building your own mansion before?
FYI, patents do not prevent someone from copying your idea. They merely give you the right to litigate. If you can’t afford a patent attorney then you can’t afford to litigate. Therefore, what is the value of your patent?
Some patents have value outside granting you the right to litigate. I’m some cases, they are a marketing tool “wow they must have great tech, it’s patented”. Sometimes it’s an asset “big Corp wants to buy me and they already have complimentary patents and they can afford to litigate. They would love to own my patent.”
I would suggest you think deeply on what your goals are and explore cost benefit of filing a patent.
FYI, if you only care about us coverage, you can file a provisional patent for about $80 and it is super informal. A provisional allows you to stake your claimed date without prosecuting the patent and spending money. It give you 18 months to figure out if you idea I’d worth patenting. But be careful, anything not covered in the provisional does not get to claim the date of provisional if added to the non-provisional filing.