It's 17:30 at the moment, the stores generally close at 18:00 so with Freya standing there you could probably manage to borrow funds and buy some "general equipment" for adventuring. Gundren would know what's needed but I will assume you asked him and all that. If you wanted to go into debt for this venture. That would indeed be a few more gold.
His cart is capable of holding 6000lbs, it's currently loaded with 1800lbs and weighs 2000lbs and each horse can comfortably pull a load of 1000lbs up a 9% grade. There aren't any grades close to that on the way to Phandalin so there's plenty of space.
If you were really industrious with the heart of a trader you could have asked around and gotten other adventurers or others to buy in for a good return. Maybe next time.
