"Major rehab" refers to an extensive process of repairing, renovating, or improving something, typically a building or property, that requires significant effort, time, and resources. Full definition
She requires major rehab which will cost more than is possible on a cab - driver's wage. (independent.ie)
If you're interested in rental properties, you could start with some «turn key» ones that don't require major rehab. (biggerpockets.com)
But a whole lot of baggage: City Demolition notice of the 9 - Unit Building, an inherited and potentially problematic tenant in the 4 - unit building, no parking for 13 - units, major rehab on both buildings, etc. etc., which made it unattractive to everyone else and two weeks away from City's fix or demolish deadline. (biggerpockets.com)