How much should I sell iPhone 5c for if SIM card slot is broken?

The SIM card want read. Always saying no sim even if SIM card is in.

In that condition it's scrap value only. As you didn't state where you're located on this planet of seven billion people it's difficult to offer useful guidance as to value. In the UK a scrap iPhone 5c in perfect cosmetic condition and powering up but otherwise non-functional would be worth up to around £40 if sold privately. With a scratched casing or a scratched screen about £25, and with both a scratched casing and damaged screen it's about £5-£10 on a good day and unsellable junk otherwise. Secondhand tech shops would offer £5-£10 at most for cash (if they offer anything at all) and as store credit about £15 if you're lucky.

Paying for a professional repair will likely cost about what the phone would be worth if it was fully functional and in excellent cosmetic condition so is not likely to be a worthwhile investment to try and add resale value.