My vote would be to buy everything...the bucket...the chipper...and the chipper truck.
The combo unit is useless unless you are working along the road. Having the chipper on the back of the bucket for residential work is a mistake in my opinion. Brush either cannot be chipped while the "bucket jockey" is doing his thing due to the positioning of the two pieces of equipment in the available area. At times, chipping can be accomplished at the same time as bucket operations, but this usually means dragging the brush all the way back to where the chipper is located. Not productive at all. Usually the chip box on a bucket carries only 1/2 of what a dedicated chipper truck handles.
I have been through this senario years ago and if I could do it over again I would have began with a bucket and a chipper/truck even if the cost is more. Sooner or later you will decide to keep bucket operations separate from chipper activity.
Another added benefit is as one job almost completed, one can take the bucket on to begin another.
Granted, licensing and insurance is an added cost but that is usually paid for in the first few jobs of the year.
Safety and productivity should also add into your equation.
I use my bucket about 3 days average out of every week about 8-9 months out of the year. This year I have made more money than previous years.
True, there is a time and place for buckets as well as climbers. But, it is soooooooooooooooooooooooooooooooooooooooooooooooooooo much easier, safer, and faster with a bucket.