I used to do a similar thing as a boy with a homeless guy who lived at the bottom of our road in a little tin hut he'd built, i
I was often in there on my knees sucking his cock and lettting him do whatever he wanted to me, He had a small cock but i didn't know any better back then so he didn't hurt much when he fucked me, I visted him often back then right up till i was thirteen when he just up and left one day and i never saw him again, Like you i still pass the spot where his hut was which is now a mall and i miss those times quite a bit.
I was 16, and my uncle owned a few acres of land next to to the rail road yard, and like yours, it was closed. The land my uncle owned was mostly wooded and kind of unsightly, but so was that whole part of the area. There was several homeless people living around there, this one had a tent set up on uncles land, unk knew he was there, but let him stay. we lived just over the hill, and one Saturday morning I was over there, I met the guy, and we started talking. He wasn't as old as he let on, he told me hot my ass looked, he showed me his dick, and I gave in to him, and he fucked me dog fashion. To my supprise, it didn't hurt, and even though I did feel embarrassed, I was loving what he was doing to me. It was unprotected and before I got home the crotch of my shorts were wet with his cum. I thought about it for a few days, and ended up going back a lot of times, but I always took condoms with me after that first time.