So, buying a domain in general...I think that is a must because it looks professional, viewers will be more likely trust your content. Expired domains though...I would do some research on that, some backlinks are bad. When I first started blogging I was apart of school type community and I was taught to not buy expired domains.
Expired domains can come with a few problems. The niche could be entirely different, just because the website is gone doesn't mean that previous content disappeared from search engines databases. You really need to make sure that the backlinks are quality and check the trustflow because you don't want to purchase an expired domain and be on the bad side of search engines because of the previous owner.
You can check MozTrust and ahrefs for information on some important factors of the domain you are looking at.