As has been stated, apply for your eTA before you travel. You can’t board a flight without it.
When you arrive at the airport, be honest with the CBSA officer. Tell them you intend to apply for inland sponsorship. Dual intent is allowed in Canada, whilst a lot of other countries don’t allow it.
If you tell them that you’re just coming for tourism and they discover you’re lying, you could easily be refused entry. Quite why some people think this is the better option, I’ve no idea. I’ve found the CBSA to be incredibly easy to deal with when I’ve travelled here. They just want honest answers to their questions.
The last time I entered Canada, I told them my wife (Canadian citizen) and I were married and that we’d be applying for inland spousal sponsorship. The CBSA officer took the time to give me a visitor record so I had a UCI to put on the application forms and my details were formally in the immigration system before my wife and I had even submitted my sponsorship application. It also allowed them to admit me on a visitor visa for 12 months, instead of the usual maximum of 6 months I’d be entitled to as a national of a visa-exempt country. I had my OWP approved within 3 months of submitting my application.
The best advice I was given, was to be honest at all stages. Don’t ever lie to a CBSA officer or IRCC official. And never lie on an application, either deliberately, or mistakenly. Double check everything you put in your application. If you’re found have deliberately misrepresented yourself on an application, you can be issued an exclusion order for up to 5 years.
This forum and the IRCC website, is full of useful information and this forum in particular, is a great resource if you get stuck on any aspect of your application. You’ll find any answer you could need here.
