Nothing is necessary. However, a USB audio interface will dramatically increase the sound quality, even with a cheap microphone.

You don't have to invest in expensive devices. Even an entry-level interface will give you enough sound clarity to do a very decent job. Focusrite Scarlett models are the best sellers for amateurs because they are reasonably priced and have very good sound and build quality. Of course there are much better interfaces with exceptionally better sound, but they are intended for people who have great microphones, more experience, know what they're looking for, and they have the skills to fully utilize them.

A Focusrite Scarlett Solo is probably less than 100$. It has one microphone input, but I guess it will work for you. If you want to use two microphones at the same time, there's Scarlett 2i2. It depends on what you want, there are other models with 4+ mic inputs.

However, if even that is expensive for you, there's no reason to avoid even cheaper alternatives. Behringer is a brand that's talked about a lot. It's a budget brand that releases products that resemble repudable brands and models. It's usually trashed quite a lot by professional audio guys on various forums. Of course their build quality and their reliability are mediocre, but it's a great solution if you are a beginner and just want something to have to do your hobby.

There's also products that are a microphone and instead of XLR/Jack outputs, they have an internal USB interface. This is a possible solution, but it's not very flexible if you later want to add something else. I would generally advise you to get a cheap interface with one or two XLR inputs and record your music before you start worrying about what the "pros" say. Pair it with a cheap microphone (~50-80$) and you'll be good to go. Later, when you get a job or something, you can upgrade your mic to something better, and even later you might have more money to invest in a better preamp/interface.

For me, it is much preferred to be able to have something, even if it's not great, than not having anything at all and not being able to do what I'm passionate about. Music is a great thing, and doing it in any way is so much more important than waiting until you have money for the perfect mic/interface/guitar/amp.

Nothing is necessary. However, a USB audio interface will dramatically increase the sound quality, even with a cheap microphone.

You don't have to invest in expensive devices. Even an entry-level interface will give you enough sound clarity to do a very decent job. Focusrite Scarlett models are the best sellers for amateurs because they are reasonably priced and have very good sound and build quality. Of course there are much better interfaces with exceptionally better sound, but they are intended for people who have great microphones, more experience, know what they're looking for, and they have the skills to fully utilize them.

A Focusrite Scarlett Solo is probably less than 100$. It has one microphone input, but I guess it will work for you. If you want to use two microphones at the same time, there's Scarlett 2i2. It depends on what you want, there are other models with 4+ mic inputs.

However, if even that is expensive for you, there's no reason to avoid even cheaper alternatives. Behringer is a brand that's talked about a lot. It's a budget brand that releases products that resemble reputable brands and models. It's usually trashed quite a lot by professional audio guys on various forums. Of course their build quality and their reliability are mediocre, but it's a great solution if you are a beginner and just want something to have to do your hobby.

There's also products that are a microphone and instead of XLR/Jack outputs, they have an internal USB interface. This is a possible solution, but it's not very flexible if you later want to add something else. I would generally advise you to get a cheap interface with one or two XLR inputs and record your music before you start worrying about what the "pros" say. Pair it with a cheap microphone (~50-80$) and you'll be good to go. Later, when you get a job or something, you can upgrade your mic to something better, and even later you might have more money to invest in a better preamp/interface.

For me, it is much preferred to be able to have something, even if it's not great, than not having anything at all and not being able to do what I'm passionate about. Music is a great thing, and doing it in any way is so much more important than waiting until you have money for the perfect mic/interface/guitar/amp.