調達 and 用意: obtaining needed materials and making them ready
Compare obtaining materials with having something ready for use. Ownership or a new purchase alone does not make the words mutually exclusive.
Obtain materials from a source
調達, read ちょうたつ, means procurement. 祭りに必要な材料を近隣の店から調達した。 says that the festival materials were procured from nearby shops.
材料 is the obtained object, and 近隣の店から its source. Read the acquisition without adding an unstated purchase cost.
Have something ready for use
用意, read ようい, means preparation. 来客のために温かいお茶を用意しました。 says that warm tea was prepared for the guests.
The tea-preparation action is completed. The sentence does not specify when or where its ingredients were purchased.
Obtaining and preparing can overlap
Obtained materials can be made ready for use, so the acquisition and preparation perspectives can apply together. Check the source and the purpose separately.
Do not restrict 用意 to previously owned things or 調達 to newly paid purchases. The contrast in these examples concerns obtaining something and making it ready.
Is 用意 necessarily wrong for materials that were newly procured?
Show the answer and why
No. Obtaining the needed materials and preparing them for use can describe aspects of the same situation.