You are free to receive as many smartphone keys as required for unlocking doors, cars, boxes and other Tapkey-enabled access products. Using the Tapkey app will always be free.
People who grant access to you (“Lock Owners” such as home owners, employers, hotels, car rental companies etc.) can issue an unlimited number of smartphone keys for you. Tapkey will charge lock owners for smartphone leys, so costs will never arise for those who receive them.