FYI, SpaceX developed all of their engines in-house[1]. Other American rocket companies use Russian engines and Congress's bill forbidding that going forward has put ULA in a very bad place because Blue Origin's BE-4 engine still is not ready after more than a decade of development.
He wanted to buy some Russian rockets to send a greenhouse to Mars, but they did not take him very seriously and quoted very high prices. After that is when he got serious about starting SpaceX.
[1]https://en.wikipedia.org/wiki/SpaceX_rocket_engines