I don't think communism is a moneyless system. Pretty sure people paid money for things in the USSR. Have there been any communist countries without money?
To understand this you need to understand the theory. Marx outlined that socialism and communism each had to be transitioned to after reaching a given level of social/economic development. In particular there is the notion of "withering away of the state" which would happen after a global revolution, which is the aim of this classless/moniless society they outlined.
The communist manifesto is a short read!
In fact the USSR implemented explicit market policies, a sort of contained capitalism, which was designed to facilitate reaching the necessary preconditions for socialism and communism. Essentially all of the "communist" states we've seen so far have been some play on the notion of just "socialism in one country" in the Marxist-Leninist version of communist parties, who have/had the goal of eventually reaching communism.
What's probably most interesting is that the idea behind the USSR wasn't initially to have the state direct everything from the top, but in fact to facilitate worker councils (soviets) to direct their workplaces.
But you have to remember this all happened in the context of a state which had recently undergone a revolution, was rife with counterrevolutonary action (see revolutionary France and civil war Britain to see how this played out during the birth of liberalism) and was then plunged into WW2 where most states involved were acting fairly dictatorially for the duration of it. Followed shortly by the US making it an explicit goal to prevent world communism through e.g. CIA intervention because they feared "domino theory"
Yes, which is why the USSR never once in its history claimed to have built communism. The best they claimed was "developed socialism" with promises to build Communism someday
By the time we reach Communism, that is, the Marxist vision of a fully publicly owned and planned world economy, distribution of wealth will likely be based on need. There is no necessity for equal wealth, as humans have very unequal needs. Equal ownership of property is certified through public ownership.
If you're asking what's preventing someone from starting a business, it would be the sheer difficulties of actually starting one that can compete with the highly developed productive forces in the rest of the economy. Communism isn't so much about outlawing private property, as developing beyond it.
Communism is a post-Socialist society, it must be global, highly developed, and have full public ownership, or close enough to those. The Soviet Union was, instead, Socialist, ie an economy where public ownership is the principle aspect. That being said, there were attempts at Cybernetics, and moving beyond money. These are actually incredibly interesting, and anyone interested in Socialism should look into those attempts.