There are machines around. Some of them are even rideable.
For only 400 square feet however I would suggest the EDCO chipper. It is an air powered/stand-up-and-use demolition tool. Should be able to rent one.
Removing the tile and the thinset are generally two differnt tasks. No one-tool will usually do it all.
After chipping up the tile the floor can then be ground down smooth. Again, EDCO makes machines to do that also. I would suggest their carbide toothed rotating grinder.
No, I don't work for EDCO and yes, there are other tool makers that have similar tools. My experience with the EDCO tools has been good over the years.