Well, if I suddenly found myself having to care for 17 indoor cats, I'd start by making sure they were all S/N. Then to help them acclimate to the situation:
I'd buy the biggest cat tree imaginable and also get half a dozen standalone kitty condos. Put a window perch in each window. Just things to give them some separation but it also helps their overall happiness.
I'd buy three cat water fountains. And...well, I would just massively free feed and hope for the best.
I'd get 20 litter boxes with multi-cat clumping formula. If the house is big enough, you could close off a very small room and then use it as a "special area" that the cats can't get into.
I'd buy three TurboScratchers and spread them out across the residence. I'd buy a couple of cheap rugs from Target and leave them around in the larger rooms -- cats seem to like scratching on that cheap synthetic surface. I'd get a couple dozen catnip mice and put one in each corner of the house. I'd also buy a couple Da'Birds and a couple Cat Dancers -- save those for the lethargic cats.
I'd start taking notes to figure out each cat's habits, like which cats are adjusting to the situation and which seem to be loners. If a cat seems lazy or withdrawn, I'd take that specific cat to the "special room" and engage them in an interactive game like Da'Bird or Cat Dancer. That will give the cats who need it a short burst of 10-15 minutes of individual attention each day. You could also use it as a temporary separation room if one cat is really causing a disturbance.
Finally, just to round things out, take a look at the thread about favorite cat toys:http://www.thecatsite.com/forums/showthread.php?t=46340
Consider buying or using any of those ideas that might work.
But with 17 indoor cats, you've really got your hands full! Good luck with it.