Recruitment is an absolute nightmare, I'd tread very carefully if I were you. What sort of recruitment are you looking at?
I used to work in recruitment and you'd be entering one of the most competitive industries there is. It's a thankless task to be honest. You mentioned where your wife works they use a lot of agency staff and they're always chopping and changing. That really isn't surprising. Is this the sort of work you're looking at doing? Contracts like that, that are probably minimum wage, with little or no chance of people being made permanent are a nightmare to run. Good candidates will eventually get jobs elsewhere and you're left with the merry go round of people who will always be temps. They'll turn up for a week or so, then do a disappearing act. You'll have phone calls at 5.30am in the morning from people too pissed to go to work at 6am, leaving you ringing round (and driving round) trying to find someone so your not letting your client down. Then there's the people who swear on their own lives they'll be there on time and you never hear from them again.
If you're looking at specialist recruiting, such as IT, medical, scientific or financial, then there is still some decent money to be made (not as much as there used to be though). If you're looking at supplying industrial and other minimum wage staff, then you are looking at working very, very hard for little or no reward and giving yourself a load of grief in the process.
Sorry for being quite negative, but that's the way it is really. And recruitment is changing too. Apart from running nightmare contracts like the one I've used above, what services do traditional recruitment agencies provide that a company can't realistically do themselves? This, taken into account with the rise of fixed-fee and other online recruitment based businesses will leave the traditional recruitment agency redundant if they're not careful.