How do you convert a 33 unit rental condo building to an owner occupied 50 and older retirement condo complex?

Your terminology in the question is confusing: either your building is a rental building, or it's a condominium building. Each presents different challenges for conversion.

If your building is a rental building, the owner can hire an association-savvy attorney to develop the governing documents, and work with a team to establish conversion prices, move-out arrangements for tenants who chose not to buy, and identify residents who won't be required to move.

If your building is a condominium, your association-savvy attorney can help you survey owners to identify the chances of gaining the uber-majority of votes required to amend your governing documents. Then, the attorney can draft the amendment and lead the membership through the voting process.

Again, logistical arrangements for residents who do not qualify under the new governing documents and will be required to move, must be made and implemented.