Mr. Amber Cat, "Amber," was my first cat. He was an outdoor little one I took in shortly after I moved into my apt. in RI. I lived on the 3rd floor, had a balcony. Amber did NOT like being indoors, and he made that very clear.
For the 8 years he lived with me, we had to walk around the apt. building TWICE. Not once, not three times. TWICE. He was VERY into routines, that boy. He made a fuss until I agreed to take him out; then he sat calmly while I put on the harness and leash. I always carried him out of the apt. and down the stairs, putting him down once we were outside. I did not want him to learn it was OK to walk out the apt. door! Once outside, off he went. I was ignored, and he did what I called his "tiger in the wild" performance. I was expected to be invisible, and QUIET. He had certain places he HAD to sniff, stops we had to make, gutter pipes which HAD to be peered up. If my sneakers scrunched on some sand in the parking lot, he would look over his shoulder and it was clear I was NOT to make any noise again! We had to make this walk no matter the weather: burning hot summer sun, snow, sleet, rain and ice. Once per day, more if he could "talk" me into it. But he was insistent about once per day. I let him walk in the building and up the stairs to ur apt. He ran up and I usually and to rush to keep up.

All my cats are used to harness and leash. Some walk, others won't. Get a "figure 8" harness or, if you can afford it, the "H" is the best, it has two snap closures. I have had cats slip out of Figure 8 harnesses, but never the "H" type harness.

The cat needs to adapt to the harness. The first few times you put it on, the cat will paralyze, roll over on the floor, maybe try to get it off. Start with 3 minutes, work up to 5, depends how the cat reacts. Then eventually the cat will start walking in a low-to-the-ground slink, as if s/he is carrying a 100 pound weight!!! Too funny. They WILL get used to it, especially if the cat WANTS to go out and learns to enjoy outdoor time.

I use the 10 foot retractable leashes. That way, I can keep the cat in close to me if I feel I need to, let them wander and poke if it seems OK. Sometimes I would stand talking with a neighbor; the cat wanted to sniff the bushes a few feet away. You have to learn to keep it untangled from bushes and shrubs as the cat rubs its face on the lower branches.

I often took 2 cats, Amber and Sparkle. Sparkle mostly wanted to be carried. She would walk a short time then I had to pick her up. Back then, Vita wanted nothing to do with it, she was even nervous out in the hallway of the apt. buidling - too much open space. She needed walls and a roof over her head. Chestnut didn't mind the paths and parking area, but refused to walk on the grass, he didn't like the feel of it on his toes! (Since I bought my house and moved 4 years ago, they have all adapted to the backyard and LOVE it out there.)

Problems I encountered were not from loose dogs, but from cats!! People let their cats out loose, and they would wander over and want to visit, meet, etc. Amber tried to chase all of them off. He would start this siren sound which grew in loudness and pitch, up the scale, and pounce or chase them at the high note. I would have to try and draw him away and shoo the other cat to go in a different direction. If this does happen, do NOT try to hold or pick up your cat. Drag him along on the leash and do not touch him until he has calmed down.

Balcony. I was on the third floor. Well, I guess you would call it 2.5, the lower level was below ground with their windows at ground level. I bought one of those panels you can put between the slider door and the door frame. It has a pet door in the bottom. My cats were in and out most all the time. If the weather was fine, I often went out and left it open so they could enjoy the balcony. They did enjoy walking on top of the railing, which always made me VERY nervous. I kept a string of bells hanging on the door handle. Amber learned to "ring those bells" anytime the door was closed and he wanted to go out on the balcony.

None of my cats ever jumped down. But the woman on the second floor, her cat not only jumped down but, after roaming about for hours, climbed up on the metal railing of the entry door and from that jumped up onto the balcony! So that cat came and went when he wanted to. She had bells on the OUTSIDE of her slider door so he could let her know when he was back and wanted IN.

However. When little Chestnut moved in with us, Amber pushed him off the balcony 2 different times. Fortunately we had a row of evergreens below. I would come home from work and as I passed, the bush meowed at me! The first time I couldn't figure out WHAT I was hearing! I was startled to find my little tiny kitten in there, and I thought he fell off. The older woman next door told me Amber was pushing him off, after it happened a second time.
She happened to be out on her balcony and tried hollering to Amber to stop but he just went ahead and pushed the baby off. So I had to either leave the door closed all day, or leave Chestnut closed in a bedroom. Once Chestnut got bigger, this didn't happen anymore.