Congrats on your new house!!
I have to put a disclaimer that we've never bought a new house either, and any advice I give could be wrong so please don't rely soley on what you read here because it could be wrong.
It's my understanding that they'll be calling us shortly to arrange appointments for the purchase agreements. When we get the purchase agreement we will have 7 days to then have it reviewed by our lawyer and to also get financing locked down ( I think ).
You are right in that you do not have to add/decide upgrades at the meeting where you get your purchase agreement, actually I don't think you could even if you wanted to. Upgrades come later at the design center (there are 2 types of upgrades, structural & non structural, visit the design center on Saturday! Ask them questions! They are very nice & helpful).
I don't know if people will have any luck in getting mattamy to throw in upgrades considering the line-up/demand
But please still try it doesn't hurt.
I did ask someone who bought a mattamy home already in the past what their lawyer did, they replied saying....
"Our lawyer put a cap on how much Mattamy can charge us at closing for any unforeseen problems relating to hydro/water/etc. The lawyer also changed the clause that states that Mattamy can force us to move in earlier if the house is ready. This is important because if you don't delete this clause, Mattamy can force you to move up your closing date, and if you have a home that you're selling in conjunction with this purchase, you could be in some financial trouble. I think there were some other minor changes, but I can't remember them offhand. "
...but that was a past purchase, so the purchase agreement may be different, I don' t know. Honestly I've never seen what Mattamy's purchase agreement looks like. When I get it though I will read it carefully and we already have a couple lawyers we've been referred too, but haven't picked one yet. I think the standard rate is around $700 to $800 for the lawyer (that includes looking at the purchase agreement and also all the legal work in closing). Someone also said that when you get the Purchase Agreement from Mattamy they can also recommend lawyers for you if you ask (which sounds a bit odd to me from a conflict/interest standpoint? dunno). You will need a lawyer to help close things for you anyways, so most of them will help review the purchase agreement with you and they include that cost in their package I think, it's usually not extra.
So what's next?
(1) Lawyer
(2) Bank
(3) Visit design center, think about structural upgrades first.
Btw see if you can get a upgrade or something thrown in! Doesn't hurt to negotiate. But with the big line-up and demand, Mattamy may not move much or at all.