Hello Dale,
Welcome to the Moodle Community!
As per your questions, yes you have to have a hosting company for users to use it remotely (e.g. from Home), else you can get it installed on office server (notice I wrote server and not desktop) as a common desktop will run out of resources after few users.
As per costs are concerned, it depends on following:
1) How many users you'll set up initially, with average growth rate of users monthly.
2) what type of training is involved? simple text based or Multimedia based with option to take quizzes?
3) would you be adding a member discussion forum as well?
4) how many (expected average) users will be using the system at the same time?
based on above, the costs can vary, from as low as $5 a month, up to several hundreds.
As per content is concerned, yes you can make it on desktop and later upload on to moodle server. for that, members usually use the offline moodle and create courses later to be restored on to the production server.
As per comparison is concerned, I have personally used Blackboard during my university, so the only thing I can do comparison to is Blackboard, for that I must say, Moodle stands Awesome. You can't even Imagine the possibilities!
for training, Mary have provided you with a link already, but I can understand that just reading from text won't be taking you anywhere soon, for that you can always come to forum and ask questions, and they will be answered to much of you expectancy. With that said, now is time near that I should start making video tutorials for people who are new to Moodle so they can have jump start in matter of hours.
