I'm not in the business of buying IPv4, but have worked with networking in the past.
There are two ways of acquiring address space. First, and in our case the less-relevant way is to register with a regional internet registry (RIR) and after you meet the policy and technical requirements you will be put on a waiting list to receive a small subnet allocation. You’d also need internet peering and an ASN for this.
The second and a more suitable way for an investor (instead of a tech company) is to register with a RIR and then simply purchase a subnet from a qualified facilitator and transfer it to your RIR account. Here’s a list of facilitators from an American︀ regional registry
Find a Qualified Facilitator
IPv4.Global Is a reputable site from that list, although︁ there are others. Note the $/address price and the total, based on the size of︂ the subnet being sold. After you’ve found what youre after, you will bid and pay︃ for the subnet as well as additional broker/auction fees, and RIR registration fees.
Very important︄ note is that IPv4 addresses also carry a reputation with them based on what they︅ were used for before and who used them. Before bidding on a range make sure︆ those addresses aren’t blacklisted.
After you’re an owner of an IPv4 subnet, you can for︇ example use a platform like
https://www.ipxo.com/ to lease and monetize it.