Yep - so if I had a channel and you had a channel, we'd both subscribe to each other
It doesn't help your channel though. It actually hurts it. YouTube isn't stupid and they know this

. I've seen a few people whose channel has suffered from doing it and they're struggling still to get views and subs.
There are service (people?) that can get you hundreds of subs very quick - it's tempting to if you're just starting out - but I wouldn't do it. Natural is the way to go and perseverance.
Check this out...crazy no?
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