Congrats and getting ready to dive in. A couple of thoughts, but these are all opinions as will be every other response on this topic, so mash them all together and do what's best for you.
In most good rental markets around the country buying existing properties can be done for less than building new, so there's not much motivation to build. Compare the pricing on both sides, check what the available inventory is, and go from there. Also, it can be easier to get a loan for an existing building as opposed to a construction loan if this is your first real estate endeavor.
Last, would your primary residence make a good rental? If so, hold onto it, and do a HELOC to access the equity to use for your next project.
And no, you can't do a 1031 on your primary residence, but you don't need to. If you've lived in it for at least 2 of the last 5 years, you can sell it and exclude the proceeds from your income calculation, up to $250k of gain, or $500k if married and filing jointly.