If you purchase an investment property first (and it's a smart investment with decent cash-flow), you should be able to use the income from that investment property to offset (most of) your costs, and return your debt-to-income to (close to) where it was before you purchased the property. This would allow you to purchase your primary residence afterwards.
On the other hand, if you purchase your primary residence first, your debt-to-income ratio increases, with no ability for you to bring it back down using investment income. This would make it more difficult to then purchase an investment property.
So, of these two situations, I would recommend the investment property first, and then the primary residence.
That said, there are other things to keep in mind:
- I'm not sure if the tax credit (the $8K) would be available when you purchase your primary residence, if you first purchase an investment property. That's something to look into;
- My scenario above is highly dependent on the specific financials related to: the investment property, the primary residence, and your current financial situation. Depending on all the numbers, this may or may not work out the way I said. So, run some scenarios with your mortgage broker;
- Have you considered purchasing a multi-unit property (duplex, triplex), living in one unit, and renting the other(s)? That's another option to both gain a primary residence and buy investment property simultaneously.