My Time At Portia

As the Achievement says you Must Purchase every Land Expanse for your Workshop to obtain this. Personally I don't see the point except for a Larger house, as once you have a Factory Space becomes more of a Commodity than a Necessity.

Having said that there are 7 Land Upgrades that Rise in Price.
lvl 1- Default
lvl 2- 1,500 Gols
lvl 3- 15,000
lvl 4- 30,000
lvl 5- 100,000
lvl 6- 160,000
lvl 7- 250,000

You will need to spend a Total of 565,000 Gols to unlock this.

The user Soren Kisamora is quite correct. You must pay quite the hefty sum for the maximum yard size...
...
A sum that can be reduced by as much as 25%. And a way to keep 225,000.

The first yard size or two should be your priority. You NEED bigger spaces for the assembly yard and house upgrades, to say the least.
After that, however, it's a good time to take a break from your yard, and turn your attention to marrying Gust.
Gust, at the relationship stage of "lover" (8 hearts) starts his marrying quest, and as husband, gives 25% off the A&G prices, and makes yard prices cheaper. 565k can easily turn into 415-420ish, days and days of money making/waiting for the town market to buy items for expensive.

Now, heres a bonus tip.
Marrying gust is an achievement. He gives you a ring when you marry him. KEEP IT.
Save the ring, stay married until you get the yard. If you want the yard, keep it, divorce Gust via broken mirror (typically 50k by mysterious stranger, come prepared or read next tip) to start going after Phyllis, marrying cheevo #2.
If you DON'T want the yard, exit to main menu after paying the 225,000 for the final upgrade, continue game, divorce Gust, keep ring, Go after Phyllis, have 225,000 to play around with.

This works because the game only saves when you sleep or pass out at 3:00 to be FORCED to sleep. Exit to main menu even 1 minute to 3:00, you must start the whole day over. Do the yard in the morning so you can easily decide.

Happy hunting (>*_*)>