This is JMO, but, I would go with a 36" Hydro walk-behind, or maybe even a Stander, and a 60" ZTR. The 36" will allow you to fit thru gates that others with larger mowers will pass up, plus when coupled with a sulky, it can still mow larger areas fairly efficiently. I have found that many of the LCOs around here run 48" and larger walk-behinds and won't do gated areas. The 36" enables you to get into those backyards and charge a pretty good rate because nobody else wants to do it.
Brand selection is largely dependent on what types of dealers you have nearby. If the only thing around you for 50 miles is Scag dealers, that's probably what you are going to want to use.
I don't know what exactly you are looking for in a truck, but I do know for about $4-5 grand you can get something reliable that looks respectable as well.
You'll also need a trailer to pull your equipment. I'd recommend at least a 6 x 12. That should allow you to put your walkbehind on sideways in the front and pull the ZTR in behind that.
I see you have mentioned 2 edgers in your list. What about the string trimmers? I would only get 1 edger unless you are going to be doing a ton of edging. Trimmers you will probably want to have two, but you can get away with just one to start. Just make sure the trimmers/edgers/blowers are a good name like RedMax or Shindaiwa.
This is just a little bit of info to get you started. Like Battags said, try the search function. There is a wealth of info archived here. Also check the New in the Business Forum and maybe even subscribe to some trade publications. The more you know the better off you'll be.