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HERE are the rules/procedures for a Partition in California. HERE is a form for the actual partition. This would be the pleading that is filed with the Court to begin the process.
Using counsel, the case would normally run about $5,000 minimum for attorney fees for an uncontested case (where the co-owner simply does not respond, but responds but quickly agrees to a settlement), but likely more than $5,000 for attorney fees if the case is litigated. This does not include legal fees.
Without counsel, only the legal fees remain which may run into a few thousand (filing fees, deposition, discovery, miscellaneous, etc).
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