Unless there's a lot of metal up there to reflect RF, dipoles in an attic will "work". But there is RFI to your condo and others to consider, and you won't find that out until it's up and working. How much power you run will have a lot to do with that. That's on the transmit side.
On the receive side, maybe a bigger problem. I've had six monoband dipoles in my attic since 2002, remotely switched from the shack. At first, they worked pretty well...no ductwork or HVAC in that part of the attic, and a concrete tile roof. The main problem: as the years progressed and technology advanced, the steady proliferation of household and neighbors' electronics...Wi Fi modems, DVR's, plasma and LCD TV's, computer monitors, fancy appliance electronics, newer HVAC circuitry, electronic gadgets, and their related switching power supplies and wall warts...all contributed to an ever increasing hash and noise level. So much so, that they are now practically unusable receive-wise. I now use a ground-mounted screwdriver outside, and that works much better, and keeps me on the air.
73 and stay safe, Bob K7JQ
Note: before I hit "POST", I read K0UA's comment. Kind of similar.