When you come to buying bouncy castle research and a little more research look around for all the different manufactures make a list then do your research I can not stress this point any more you will be spend a lot of money and this is your main money earner you do not want to get this wrong.
So you have your list of companies some will be very cheap I would say be wary of these time of companies they most probably be stitched once and will not last you the season.
Remember the castle will need to last you for you to regain the money you invested in it then to make you money you will also resell your castles so it needs to last and keep looking reasonable.
Also people will not like hiring a ripped castle.
You will also find companies that are very expensive these will most probably have mutable stitched.
This is great as they will last you a lot longer and will stand up to a lot more rough treatment.
These bouncys will be heaver so harder to handle on your own.
I would suggest going for something in the middles of the two looking for going for something that is going to last your 2-3 seasons a castle that is double stitched should be ok.
You would be looking at around £1500 for two brand new bouncy castles this will get you a children castle and an adult one.
I suggest you get this companions as it will open more options.