Your comments are very helpful and much appreciated!
Multiplayer wouldn't be a big issue, did this before but yes, it has to be planned from day 1 as it's completely different. Still not sure about that though, because multiplayer obviously only work when you have other players who want to play at the same time.
As for money, nowadays you can always aim for a Patreon later on down the road to get your art expenditures back... It's not a sure thing, by no means, but worth a shot, anyway, if your game ever gets a following
Haha, well yes. I know Patreon, I even support one guy there. Dunno, could work out indeed, but obviously that's still way to early. First there have to be a game and it's always questionable if it's received good or not even though when it's well made. Nowadays it's pretty difficult to get noticed at all...
@Publius: Thanks for that, didn't know it yet. I agree, stealth mechanics are not for everyone, but so are roguelikes, turn-based vs realtime, single player vs multi player and all that stuff. When I've learned something that there is always at least one guy out there who is more strange than you/me and will love what you do.