Pros:

If you Buy Twitter Followers, It’s a quick way of kickstarting your Twitter account. As opposed to starting from zero to a few dozen followers, now you’ll be launched off with a few thousand followers from the get-go.

The best part, arguably, is that it will strengthen your social credibility. Having a following means you have some Social Proof, causing new visitors to take you more seriously, engage with you online, and follow you to the point of purchase from you or your company.

Different Marketing Campaigns are visibly more effective. That’s a fact. The more followers you have gives you the “bandwagon effect” casting less doubt about your business. This helps both save in the long-run.
Social Proof can increase conversion by up to 1400%. Showcase your large following on your website and show others how many people love your brand. This is no joke – source.

Gain more organic followers as a result of your positive social proof. When you have thousands of followers, users are more likely to perceive you as “worth following”.

Attract more impressions and engagements – With a larger following, your tweets are able to reach a larger audience and attract more engagements. This doesn’t work with shitty tweets.

If you’re a professional, artist or a small agency, the number of followers you have can affect how potential clients, fans and/or record-labels preserve you. More followers can help make the deal or give you an upper-hand in negotiating.

Cons:

The Buying Twitter Followers are typically not relevant or targeted. While many companies offer geo-targeting options, most of the followers you buy will not directly cause more sales, leads or clicks.

You can lose the followers you buy later on. This is especially true with cheaper providers and fake followers as Twitter removes them. It is important to note that some companies do offer replacement guarantees.

Buying Twitter followers is seen as a shortcut, so you’ll want to keep the transaction a secret, assuming you follow through with it.