I'm surprised your attorney, assuming you have one, didn't get a full set of condo docs to review before you signed a P&S. It's never a good idea to rely on third party representations as to what may or may not be contained in condo docs. Is there a pet policy? What is the % of ownership? What are your voting rights and what % majority is required for changes to docs, amendments or assessments? I think you need to take a step back and make sure you have the answers to these and other questions. The lack of condo docs and the fact that there are delinquent owners puts up a big red flag to me. I strongly advise further investigation on your part.
Most legal advisors, which i am not, have experience and know how to get the best info more quickly than you have experienced.
Less than 15% is a pretty strict criteria.
You might call afew banks and see if that is specific to your lender or a standard across the industry.
A local bank may have different criteria if they are not selling the loan on the secondary market.
However, >15% delinquent owners in a condo may be a tell or a larger problem in that complex.
Are the fees too high?
Is there internal fighting / disputes?
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You may also ask yourself if you want to become a homeowner in an association that has owners delinquent on their fees. I would take a very close look at the financial statements and make sure that the association has enough to cover expenses if unit owners don't pay. Otherwise you may be carrying more than your fair share of water/sewer and master insurance, let alone maintenance costs. Especially if it is a small association.
Find out why they are in arrears, if there is a plan to become current and what your share would be if the same unit owner(s) do not pay again in the future.
I think the answer to your question may vary depending on the lender you are with. If it becomes a permanent issue I do have a product that allows for >15% of the fees being past due. Happy to answer any other questions you might have.