Young Canadian, want to sponsor American boyfriend

Try reading through the information on the US2Canada website to get an overview of the process of sponsoring a spouse to Canada.  If you and your bf get married, or become common-law partners by co-habitating for at least one continuous year, he is eligible to be sponsored by you for permanent status.  It's easier if you're married because then you don't have the additional burden of proving your common-law status - the legal marriage qualifies the applicant to be sponsored.

So once he's eligible, you can submit the application and then he can come to Canada to wait out the processing.  They will document him on a Visitor Record (you need to be accompanying him to vouch for the relationship and you intent to sponsor), but the VR prohibits him from working or attending school.  He'll also probably not be eligible for healthcare benefits. 

The application process takes about a year to finalize.  You would not want to apply via the "inland" process because it requires that he remain in Canada for the duration of the application, and there is no right to appeal a refusal.  You can submit an "outland" application, even if he's staying with you in Canada, and that allows him to leave Canada during the process if needed.

I encourage you to read through the info on US2Canada, and then come back with more questions. 

He can work in the country where he is a citizen.

He can't work or study in another country unless authorized by Immigration. Just because he is an American, he can't just walk into another country and begin work.
With respect to Canada, he is a "foreigner".

You better do some reading at www.cic.gc.ca it has all the information.

With respect to working, you indicate he has a college degree.  If it is in the proper field, he may be able to obtain a NAFTA work permit.  There are numerous fields that qualify and it avoids the need of the hiring employer to obtain a Labour Market Opinion (LMO) letter.

Thus, a NAFTA qualified job allows the employer to issue an offer letter - no LMO required.  The US citizen then shows up at the Port of Entry, shows the offer letter for a job requiring the skills of one or more NAFTA category, proves his/her qualifications for the job, provides the obligatory pictures, the work permit application and the $150 fee and they issue the work permit on the spot.

This doesn't work for everyone, but if it does, it's a straight-forward way to be together while they are processing the application.

If you apply outland, he can remain in the US and live/work there while the application is being processed. It does not matter which country you marry in.

Regardless of whether he comes to Canada as a visitor or remains in the US while his application is being processed, you should definitely select the outland application route. It's much faster for Americans than inland.

It's a separate application process from inland. And for outland - all applications are sent to the Mississauga office (they are sent to Vegreville for inland).