First, Welcome Back! Long time, no see!

Since the app won't even start, there's not too much I can suggest. Only thing directly related might be to rename the ".plist" file. Just add something like "old-" to the front of it. Or even move the whole file onto the Desktop. It can be found in the "userName/Library/Preferences/com.apple.Safari.plist" where "userName" is the name of the user account that was set up originally by the owner. It's usually the icon in the Finder Window's Sidebar with a 'house' image. Click that, then look for a folder called "Library" and so on down the path to .plist file.
After renaming or moving that file, try starting Safari again. It should automatically recreate that plist file but without any corruption that may have been in the old one. If things work, you're good to go. However, it might not be a bad idea to use the "Reset Safari"
and the "Empty Caches" items in the Safari menu. Next make sure the site/file you want to use as the 'home' page is actually available.
If the above file renaming/moving doesn't work, there are some more things we can try.
Please let us know how things go. And include the version of the OS as well as for Safari.
Thanks for the friendly welcome - you gave me a big smile.
I will pass along your thoughts and advice to my friend and will let you know how it goes. It all sounds so logical!
Best ....