The cheap Harbor Freight grinders are pretty good for the price.
I have gotten lots of use out of a cheap Harbor Freight grinder that I paid $12.00 for on sale and I used it a lot and got my money's worth.
The Harbor Freight grinder lasted me a year of near constant use and more than paid for itself.
Eventually the gears stripped out and although the motor still worked great it was finished.
I just went got another cheap one again on sale.
It's not worth my time to return it.
I just throw the old Harbor Freight grinder into the scrap pile and get another one.
They are cheap for a reason as the Harbor Freight grinders are not built very good but for the average home user they work great.
If you're running a business then get a good quality grinder as they can last a lot longer.
My dad has a Makita Angle Grinder that is around 30 years old and it works just fine.