I have friends in HO Scale and they are rivet counters, two RAIL is not real, three rail is TOY...Well, I had a good friend over last week that has a 35' by 50' HO layout that had never seen my layout. He, runs DCC, has several thousand cars, several hundred Diesels, loves his Scale. What he saw different was, mine is totally Lionel Legacy, I could start up any of 15 or so Engines on the track, or lash ups, or program turnouts or even open blocks, it was EASIER....He was amazed at the Quality that LIONEL has achieved over the years....You could actually see the fine Detailing...It was a Wow for him....
So, to Answer your Question, You do need a good bit of space, a modest amount of money, and to help keep your budget in retrospect, model 1 or 2 railroads, maybe 1950 to 1975....If you choose small Steam, or small Diesels, you could get away with 054 or 063 curve diameter...Remember, Railroads start small and Grow.
In comparison, if you Join a Nice Country Club to Play Golf, (Golf Clubs and balls are Expensive) well, that's also costly. If you buy a nice Boat,(Wow, HUGH investment) and lots of fishing Gear, well, that's also Costly...If you look at Model Railroading like that, it's not that costly.
Yes, we must consider our wives opinion, (Cheaper to Keep HER), but when we are working on our trains, we are at Home....When I am in the basement, I am under her feet, so to speak......For the record, my wife is not into trains, but she supports my love for trains...Actually, I win a lot of trains????....
Lionel, MTH, ATLAS O, 3Rd RAIL, SUNSET MODELS, really hold a good resale Value.
GOOD LUCK, You will me a lot of great people, You will have a lot of Fun..