I actually went through this process with ARIN. So I can give you that perspective. It wasn't a big deal, the only minor concern I had was it felt like you're encouraged to sign up under a business entity. I had an LLC, so it was natural just to use that. I don't know what kind of vetting they do if you decide to use yourself as an organization though instead of a different legal entity.
You need to provide justification, and frankly it's not that big of a challenge to get a /22 which is what I got. As long as you can show how you would like to use them and over what time frame, they will allow you to go through with the acquisition. An ASN is not required to get any IP block. You can always associate your IPs with any ASN that you want so long as that ASN owner is cooperating with you. I went ahead and grabbed an ASN for ease but some ISPs will allow you to use their ASN.
You also do not have to purchase an IPv4 block from someone. You can go through the normal IPv4 request process, however the waitlist [1] is now over a year long for IPv4. However IPv6 are given out very quickly. IPs you acquire this way are "free" to acquire with your ARIN membership. Your membership dues are determined by the assets you hold, there is a fee schedule [2] and you need to pay it annually to maintain your membership and ASN/IP assignments.
I encourage anyone interested in understanding this process to go through it, it didn't take a ton of time nor did it cost a lot in the grand scheme of things. Being an ARIN member also entitles you to be a part of how IPs are governed in the region you acquired them in. They will occasionally send out surveys and you can vote on issues.
[1] https://www.arin.net/resources/guide/ipv4/waiting_list/
[2] https://www.arin.net/resources/fees/fee_schedule/
You need to provide justification, and frankly it's not that big of a challenge to get a /22 which is what I got. As long as you can show how you would like to use them and over what time frame, they will allow you to go through with the acquisition. An ASN is not required to get any IP block. You can always associate your IPs with any ASN that you want so long as that ASN owner is cooperating with you. I went ahead and grabbed an ASN for ease but some ISPs will allow you to use their ASN.
You also do not have to purchase an IPv4 block from someone. You can go through the normal IPv4 request process, however the waitlist [1] is now over a year long for IPv4. However IPv6 are given out very quickly. IPs you acquire this way are "free" to acquire with your ARIN membership. Your membership dues are determined by the assets you hold, there is a fee schedule [2] and you need to pay it annually to maintain your membership and ASN/IP assignments.
I encourage anyone interested in understanding this process to go through it, it didn't take a ton of time nor did it cost a lot in the grand scheme of things. Being an ARIN member also entitles you to be a part of how IPs are governed in the region you acquired them in. They will occasionally send out surveys and you can vote on issues.
[1] https://www.arin.net/resources/guide/ipv4/waiting_list/
[2] https://www.arin.net/resources/fees/fee_schedule/