Hello
I can make design of this device for you, with storage of information on SD-card.
For adding of new user scanning of "admin"'s fingerprint will be used.
Will you need to delete user from database? For that case you will need some interface (for example, small LCD-screen and keyboard). In that case price will be highier.
I will make the code with demonstration of video of working device.
Also i will provide help during assembling on your side.
Storage of database on PC is also possible, but you will need to connect that device to computer permanently. In that case you have lot of different variants (Ethernet, WiFi etc.), and details and price require some discussion.
The combination of variants (use SD for storage, the device itself for learning of new user and PC with cardreader for editing and deletion of users from SD-card) is most simple variant. For that variant price will be the same.
With best regards.
Maxim