Upgrading plot from Small to Medium

[Dustytome]

I mean is there anything that proves any of this, I really don't want to turn around to have wasted money to only see I could have saved as soon as Medium open.

The permit cost is specific to house size, so put down a house before you relocate or you'll be paying the price for a medium permit instead of small. As for the 30% part, this is the introduction of relocation. Some info is a little outdated, such as area restricted parts switching over as the restrictions were recently removed for those and they'll just get upgraded/downgraded to the proper size. [edit: oops, didn't see Jojoya's post with that already, sorry!]

Don't forget that after 48 hours without a house the plot will be freed up through demolition.
This will be mentioned in the help text for housing and when you purchase your plot.

It's just the standard 45 days, because you have to enter the house to reset the auto-demolition timer and no house exists with which to enter.