If you landed as a "single" you could always get married after landing and then sponsor your spouse, yes. However, be careful saying you're "single." If you're living with your fiance (boyfriend/girlfriend) and have done so for over a year (common-law), you must declare that when you land, and you would NOT be considered single in this case. If you are common-law and you put "single" because you are landing before marriage, you will have problems later with PR processing for your spouse because you both have to list your addresses of where you've lived over the last certain number of years. If you've lived together and did not report it - that's misrepresentation and you will not be able to sponsor your spouse and may even lose your PR.
Secondly, if you are living with your S.O., you will want to mention that probably when you apply for PR because you will need to prove a genuine relationship... so saying "single" when landing, and then applying PR and saying "we lived together for 3 years so it's a real relationship" won't cut it.
If you are not common-law though and not living together (application for PR asks if you live with anyone), you land as single, THEN marry and sponsor your spouse, this could be ok assuming you have proof of your relationship.
Hope that helps
