Ask that question explicitly and get the answer in the contract. InterLIR Global says it maintains the RIR abuse mailbox and responds to complaints during active leases, which at least shows they take the issue seriously. Whether a flagged block becomes 'your problem' depends on the terms, so get remediation timelines in writing. Before leasing any
IPv4 range, check its history yourself, and ask whether it ever hosted mail or scraping workloads. If a block gets flagged during the lease, you want the right to swap it for another one without paying twice, so ask for that too. Also check whether the abuse mailbox covers both email and web complaints.