What are the benefits and obligations of a world that joins the Federation?

Question

I've seen numerous questions about the requisites for a given civilization to join the United Federation of Planets, and this is mentioned in some episodes of The Next Generation.

However, in the end, I assume that joining the Federation is a political agreement, much like joining European Union is. As such, there must be certain benefits a world gets by joining the Federation (otherwise the wouldn't) and, at the same time, that would probably carry some obligations (maybe economical, law related, scientific?).

Are these specified or mentioned anywhere and if so, what are they?

To clarify, I’m looking not for requirements to join but concrete benefits and obligations like for example:

1. You have access to all scientific research from the Federation
2. You must disclose all your scientific research
3. You must “contribute” x number of resources to the common “budget”
4. You can request mediation at any conflict and Federation law applies
5. You’re bound to accept the Federation supreme tribunal as the final conflict resolution maker on legal issues

Happy to consider novels in addition to canon as answers.

Answer 1

The two main benefits of the Federation are

Military

Starfleet is a formidable force, with most of its starships capable of posing a threat to almost anything in the Alpha quadrant. In this way, Starfleet is more like NATO, where you retain sovereignty but are obliged to contribute towards your common defense. Attacking a Federation world obliges a response by Starfleet.

Technology

No society can join unless it is warp capable (the TNG episode First Contact involves contacting a society that is on the cusp of that breakthrough). Otherwise, the Prime Directive applies, where they cannot reveal themselves, or their technology.

Obligations

We don't see much in the way of a full list, but we do know a few things

You need a unified society for the most part. Admissions of societies that were not unified were uncommon, and done under an "associate" membership (TNG Attached)

PICARD: Every member of the Federation entered as a unified world, and that unity said something about them. That they had resolved certain social and political differences and they were now ready to become part of a larger community.

Those divisions basically sink the application of the Kes

RIKER: That's it! I can see that diplomacy is not going to get us anywhere today, and I do not have time for to negotiate. So let's put all of our cards on the table. You're concerned the Kes are going to be admitted to the Federation.
LORIN: Correct.
RIKER: As First Officer of the Enterprise I think I can promise you that's not going to happen. The Kes will be denied membership.
MAURIC: You have no authority to make that decision. Despite whatever games you played with the Prytt when you arrived, we still plan to take our petition directly to the Federation Council. They'll listen
RIKER: They will also listen to the reports of the Captain of the Enterprise and his First Officer. And I can tell you right now the First Officer's report will go something like this. Kesprytt, a deeply troubled world with social, political, and military problems they have yet to resolve. The Kes, while a friendly and democratic people, are driven by suspicion, deviousness, and paranoia. It is the opinion of this officer they are not ready for membership.

The Federation also has certain moral standards. Among them are prohibitions against slavery (Picard isn't happy with the enslavement in Encounter at Farpoint). It's presumed that anyone joining the Federation will abide by the Federation Constitution and/or the Federation Charter. From DS9:Accession

SISKO: You realise that caste-based discrimination goes against the Federation charter. If Bajor returns to the D'jarra system, I have no doubt that its petition to join the Federation will be rejected.

Valorum has a list of denied Federation applications

Answer 2

There's one benefit that is expressly given:

Citizens of member worlds can attend Starfleet Academy without an endorsement.

This is important for a major point in the life of Nog. In the DS9 episode Heart of Stone, Nog wants to attend but, as a non-Federation citizen (he is Ferengi), he must get an endorsement from a command-level Starfleet officer.

Answer 3

Not based on any canon, but one can only infer that the benefits and obligations of planetary Federation membership largely parallel the membership of autonomous states/provinces within a country. Starfleet as a military and logistical resource would come to the aid/defense of any member world threatened by hostile action or natural disaster. However, that protection and support requires resources, so there would presumably need to be some form of taxation or material contribution in lieu of taxation to keep Starfleet equipped, staffed, and provisioned. There are canon references (if sometimes vague) of Starfleet / the Federation providing aid to developing or struggling worlds, as well as disaster relief and defense against military threats. In TOS "Devil in the Dark", it's clear that the mining colony is supplying the Federation, and although the episode ends with Kirk's remark that the colonists can look forward to a wealthy future thanks to help from the Horta brood, there is no clarity on what the actual terms of trade are, but one might infer certain possibilities.

Answer 4

To answer that, we need to ask first what kind of institution is the Federation and how do you actually join. I would consider the Federation Itself as some kind of interplanetary super-EU.

What is the EU? It's a federation of independent states bounded by treaties and laws.

The same is true for the Federation. There are many member worlds (which are at least partially independent. At least during the days of TOS, there were still embassies of member planets on other member planets, similar to member countries of the EU. See: TMP: Kirk is sending the condolence greetings to the family of commander Sonak.) who joined after negotiating. It would make sense that they would sign the Federation Charta and other treaties, so the people in power over the planet (the government, legislative and judicative) would transfer power to the Federation instances of them on earth (President of the Federation, Federation Council and High Court). Everything would fall under Federation law, so laws not consistent would have to be changed. However, local traditions and customs are protected. For example, Romulan Ale was banned in Federation Space (see: Star Trek II - The Wrath of Khan). The military and similar institutions would be integrated in Starfleet. Even though not stated in canon, this seems logical because we see no dedicated military personnel that is under direct command of a member planet (so, there are no MACOS (an earth unit) in other series than ENT and dedicated non-civilian from Vulcan, Tellarite or Earth).

Imagine, when a small planet like suddenly has access to the large resources of the Federation. If you face a pandemic - no problem, starfleet will send its best researchers and doctors. You need the logistic to produce billions of doses of vaccines - the Federation has replicators. The Romulans are attacking you - they'll send you some escort vessels. You want to have a thriving economy - trade tax-free with several hundreds of worlds.