@Mindy Jensen Our firm is heavily involved in OZ's.
Couple comments:
1. You do not have to do anything for your 2018 tax return, however you will need to file Form 8996 to register as a Qualified Opportunity Fund prior to making the investment as all investments must be made through a QOZ Fund.
2. You will not pay any taxes on the stock gain until 12/31/2026 or until you sell the asset, whichever comes first. Your initial stock capital gain will be reduced to 85% after a 7 year hold period. Once you hold the business/property 10+ years all the appreciation is tax free.
3. You need to significantly improve the property by investing 100% of the purchase price back into the property.
This might help: https://www.irs.gov/pub/irs-drop/reg-115420-18.pdf
See the bottom of page 62 for the substantial improvement requirement. You have 30 months after acquiring the property to complete the improvements.
Let me know if you have further questions.