After unpleasant experiences with other hosts, I am leaning toward Xojo Cloud to host my critical back office, but I need to be able to store files accessible only to the Xojo apps (not in web space).
From reading this section of the forum, I understand SharedDocuments seem to be what I am after: not visible from the web.
My question is how I would place files there. I remember reading FTP is not available.
If I can host my files, I will order Xojo Cloud 
Hi Michel - In the Xojo Cloud control panel you can enable SFTP then upload your files to SharedDocuments with a FTP client.
Your Xojo web app can also place files in SharedDocuments with SpecialFolder: SpecialFolder — Xojo documentation
Great. Thank you Jason
It was rather easy to deploy my apps. A Paypal IPN listener, and an app for customers to download their purchases.
The only issue I had was with handleURL for the listener, but I found the solution in this channel.
It’s nice to hear that you got it working!