What Size Photos Do You Upload To Website?

Originally I was thinking of uploading the full resolution. And I might actually need this for clients who purchase digital images; however, if I upload all the full res images it won't take long until my 50 megs are gone and I have to upgrade my package, what is the best practices for this?

You can either upload what size you want them to download (doesn't have to be the original size) and they can download their photos immediately after purchasing, 

or

There is an option with download products " Do not allow download until I upload a replacement file or manually approve it. ". Which means you can replace the photos on the order with the large download files then notify the customer their downloads are ready. 

This way you can upload smaller photos or check the option to discard original files when uploading.

Great, thank  you very much for your prompt answer(s)