In countries like the USA or Germany, where the government has emergency banning powers, a research chemical can be declared illegal immediately, so a drug can become illegal overnight without you knowing it. If you plan to keep around research chemicals, its up to you to keep up with changes in the law. A key concept to keep in mind is that you can be arrested, charged, and your property seized in the United States based on simply the presumption that you possess a scheduled substance. Analog prosecutions are expensive and tend to be reserved to punish sales, but simple possession can lead to very awful consequences, even if a felony conviction isn't the final result. Perhaps your cousin Jimmy Bob's friend Gomer has some and will give you a sample.
Many people get research chemicals by discretely asking trusted friends.
Its not a good idea to go posting around Internet drug sites asking where you can get things, for several reasons. One, this attracts attention, which could speed up making a new drug illegal. Two, discussions like this tend to get repetetive and noisy, attract spammers and scammers, and are generally considered rude. Many underground researchers find companies by searching the net, but most find chemicals through friends. Beware of those selling chemicals at parties or clubs, they are notoriously the worst quality and least likely to be accurately represented.