Is the cost basis of my condo rental reduced by land value? If so how would that land portion of the purchase price be determined ? No Land Value on prop tax bill.

No, there is no reduction of your cost basis for depreciation purposes.  A condominium unit has no land value attached. When you purchased your condo unit, you were buying only the unit itself and not the land under the building. Once you own the unit, you own a fractional percentage of the land as “tenants-in-common” with the other unit owners.

no cost basis for the land? then who owns the land.  

i have done contractors that do condo projects and when they sold a house they expensed the cost of the house and a portion of the cost of the land they bought to build on.  and title conveyance also included the land so who owns the land.   even when a condo association (non profit)  owns the land its the condo association members that own the land. and that changes when a condo unit is sold.  future how could a condo owner have to pay real estate taxes on the value of their condo and land if they don't own the land.