dont be silly, who says you have to have a loft to hang lights from a ceiling, ok lets start by assuming your floor and ceiling joists run front to back of house (not side to side) that is the normal set up front wall to back, and lets assume you have not bought an electric joist finder, if you get an electric screwdriver and large sharp screw you can screw in to the ceiling looking for joists start at the side of the room there is always a joist right beside a wall, when your screw goes in if you miss the screw will not start to get tight so remove it and move sideways away from the wall an inch, and screw it in there, keep going until the screw gets tight in a joist and mark it, then move 18 inches over as they are usually 18 inches or 450mm apart make sure you are not just catching the very edge of a joist by moving the screw a little sideways and keep repeating until you know where the centre of the joist is they are usually 50mm to 100mm wide and 100mm to 200mm high these will support you, your lights, your floor and your kids swing, your punch bag, and set of hanging scales to weigh your weed. dont worry about little holes in your ceiling these can be filled with filler and a wall scraper and repainted anytime.