Federal bank regulators made clear on Thursday what investors eying financial companies had long suspected: Bring money, experience and a skeleton-free closet. The Federal Deposit Insurance Corp. on Thursday laid out a set of basic guidelines for private investors that are interested in acquiring dozens of banks that are struggling or have failed. One of the most stringent safeguards is a proposal for the acquired bank to maintain a Tier 1 leverage ratio of 15% for at least three years after the deal is closed to ensure that the bank is "very well capitalized." FDIC Chairwoman Sheila Bair acknowledged that the proposal would be "contentious," but added that she is "open minded" to negotiations through a comment period which will last about a month. The FDIC is also seeking to limit opaque interactions between financial institutions owned by the same investor groups, and to ensure that one troubled bank does not bring down all of those owned by one entity. Investors must agree to guarantee all the institutions in which they hold significant interests, and limit transactions between affiliates. It also proposes limits on "secrecy law jurisdiction vehicles," mostly offshore entities that operate outside the realm of U.S. banking law. The FDIC is also seeking commitments to unspecified disclosures about the takeover target and other entities the investor holds. A wave of bank failures kicked off last summer, after IndyMac, a large California thrift, collapsed from the weight of bad subprime loans. Since then, 65 more banks and thrifts have failed and more are expected to go under in the coming months.