Advice? Don't! Run now, save yourselves, your lives will never be your own again!
Seriously, if you are determined to do this, your local authority will have full details of kennel design/requirements which are very strict, but if you want to learn a lot this book by David Cavill is very comprehensive:
http://www.corsini.co.uk/cavill/publications.h tm
Owning kennels would be ideal if it was just the dogs, its the owners that give you the grief.
My advice would be to keep it small, keep it exclusive and charge a lot! There are people who don't really want to leave their dogs and will pay good money for them to be looked after and given luxuries such as armchairs and carpets and a TV (yes, seriously!). Gear it to the top end of the market and you will have more money for less work.
Its what I would do if I was ever daft enough to want to run kennels again.