Roblox private servers are switched on per experience, not per account. Here is how to create and configure one, what it costs, and exactly where to check whether Dandy's World offers one at all.
A private server is your own copy of an experience that only you and the people you invite can enter. It is the usual fix for "I just want to run this with my friends and nobody else", and it is worth understanding one thing before anything else: private servers are a feature each experience's developer chooses to enable. If the creator has not turned it on, there is no way to force one to appear - not with Robux, not with a setting, not with a third-party tool.
The flow is the same on PC, mobile and console. Roblox Plus members get free private servers in supported experiences, which is worth checking before you pay.
The price is set entirely by the developer. Some experiences offer private servers for free; others charge a monthly Robux fee that can be a token amount or a few hundred. Where a fee applies it renews on the same date each month, and you can cancel auto-renewal at any time and keep the server until the period you paid for ends. Roblox does not refund a private server purchase.
In the server configuration you can generally allow friends, invite specific players by username, or generate a shareable link. A generated link works for anyone who has it, so only share it with people you actually want in the server.
We have not been able to verify that Dandy's World currently offers a private server option, and we are not going to claim one exists. Check it directly: open the Dandy's World page on Roblox, scroll to the Servers section, and look for the Private Servers area. If the button is there, the flow above will work; if it is not, the developer has not enabled it and no workaround exists.
Dandy's World is built around co-op runs - you and a team of Toons completing Machines and reaching the elevator before the Twisteds catch you - so a private server, where available, is mostly useful for running floors with a fixed group rather than with random players.