Alchemist Profession Clarification

I need some clarification on the Alchemy profession and the potions it can be used to make. The main problem I have is that it is unclear how the seeds come into effect with these potions and potion supplies.

Are the seeds needed and consumed only when the potion supply is bought? Say if the alchemist managed to grow and cultivate enough to create a supply of potions. This makes sense for balance and has the potion supply act similar to a bomb bag with an additional one time cost in seeds, but makes little sense in logic, as one or two logical couldn't make the perhaps dozens of potions an alchemist would make and use in their career, or would assume that the seeds can be somewhat easily cultivated. Or is the seed supply included in the cost of the potion supply, so they wouldn't be needed at any point to make for an alchemist character who bought the specific potion supply.

Or are the seeds needed each time the alchemist wants to make a potion, in which case the alchemist has to buy the ingredients for every single potion he makes, the "supply" merely acting as say a recipe to make the potion from the seeds. While this would make logical sense in that the alchemist would always need new ingredients for each potion, it also makes the career severely under powered and costly, meaning it would be not worth it for most players as the cost alone would probably take the character's entire earnings. This especially doesn't make sense if the single potion cost doesn't need the seeds, as say the potion of flight would cost more to make than buy, making the treasure detrimental to the character as opposed to beneficial or even just useless.

Are the seeds needed when buying only a single potion, (are they included in the cost listed or are they an extra cost for each potion). If they are needed than the "potion" cost would only be the cost for mixing them, whereas alchemists would usually keep a stock of potions to buy simply or wouldn't be needed anyway if found or looted.

Also, under the alchemy profession it says that a lvl. 7 alchemist learns how to make a Toado, I'm assuming that they need to pay the 100 rupees listed with the treasure to be able to do this, and it is not given freely like many other potion recipes.

Also as an unrelated question, can an alchemist make mundane medicines and poisons (relative to their level of course) for free? Is this ability included in the alchemist profession as a side benefit?

Sorry if this post seems to ramble a bit, but I would like this clarified as I am making a character I intend to be an alchemist and would like this clarified before I submit it.