inherited a tank, fishless cycling now

In your case, your fishless cycling is done. The nitrate is supposed to be there as the final product of aquarium nitrogen cycle, and it should be 100% safe for fish as long as you keep it under 40ppm.

The only thing you need to do now is to lower the nitrate before adding the fish. It might require you to do much larger percentage water change than mere 50%. Try 70% water change a few times in a row on the same day, and it should do it.

Congradulation on completing your first fishless cycling.