Keep anything you might have to prove
Signed leases, move-in and move-out photos, receipts and invoices, insurance policies, inspection reports, notices you served, correspondence that mattered. If a version of the future exists where someone asks you to substantiate it, keep it.
The filter is not "is this important". It is "could I be asked to show this". Those are different, and the second one is broader.
How long to keep it
The safe default most landlords land on is seven years, matching common tax record-keeping guidance. For tenancy documents specifically, the practical floor is the length of the tenancy plus your local limitation period for civil claims.
Rules vary by jurisdiction, so check your own rather than trusting a number from a blog. Where a document supports a tax position, the tax retention period usually governs, and it is usually the longer of the two.
Why folders fail
"It is somewhere in my Drive" is the failure mode, and it is not a discipline problem. Folder trees force you to pick one filing dimension. A move-out photo belongs to a property, a unit, a lease, a tenant and a date, and a folder makes you choose one and lose the rest.
The second failure is separation. The receipt sits in Drive, the expense sits in a spreadsheet, and the lease sits in email. Assembling evidence means opening three places and hoping the names still match.
Attach, do not file
The fix is to attach each document to the thing it is about: the property, the unit, or the lease. Then retrieval follows the question you are actually asking, which is almost always "show me everything about this unit" rather than "show me my 2024 folder".
A document attached to a dated timeline event gets both: the file and the story of when it happened.
In UnitDocs
Open Documents, click Upload Document, pick the file, choose the property, unit or lease to attach it to, and save. PDFs, images and video are supported, and the file becomes searchable alongside everything else on that unit.