So,basically everything Max said above,plus a few of my own pointers:
your base isn't going to "go unnoticed" so disabuse yourself of that notion now
the game world is pretty massive but also fairly active,it may take days or weeks,but honestly nomatter where you settle SOMEONE is going to wander by your base sooner or later. as Max said you can try to use the terrain to your advantage,as most people will skirt a wide river or steep cliffsides before they attempt swimming/climbing (in most cases). however in the current mechanic the "defender" or base has an arguable advantage.stick to building reasonable defenses per your skill level as you progress and keep your things ALL on your claim and actually you should go relatively unmolested. if you want to try to "hide" or not attract attention, then my advice is get you mine opened and with support beams(even if you arent ready to "mine" yet) and put as much of the builds/storage underground or in your house(s) as possible,even if someone IS strong enough to risk breaching your claim,if they dont see much potential loot,theyre HIGHLY unlikely to risk the bile drain/stocks/death/etc just to peek further.
Speaking on placement,you've guessed it,darkness and twilight is exactly where alot of vets gather/settle,including the witches.
Also,as max alludes there are some nasty "Monster" variants of standard mobs and even uniques,that CAN and WILL kill you,whereas common mobs at worst will knock you out,The rats he mentioned will disease you and thats a huge headache you dont want starting out (in fact,without intervention of some powerful friends,it's also likely fatal) TBH i would advocate setting up shop right outside providence,Yes, you will see more traffic but as previously stated with proper defenses and precautions it shouldnt matter much or at all,and the fruit bushes/small game/foreagables of worth tend to be MUCH more plentiful in and around the town.
A couple of the most important things about base location is access to "natural resources" (building material) you will save yourself alot of time and headache if you build close enough to water so you arent hauling buckets for hours at a trip,and with some trees still standing not only for lumber but to leave a couple standing for branches to fuel your stoves/kilns etc. Speaking of kilns,a clay pit within a few screens of base or so is great,you can make clay yourself out of dirt if not,but it adds ALOT of time and processes to an endeavor otherwise fast and simple. It also takes quite a bit of LIME which brings me to the next item:you MUST build near lime,as you are going to require it for MANY tasks (smelting your ore,tanning skins to leathers,building stone hedge,possibly making clay from dirt,etc) so you CAN opt to deal with an extra chore to circumvent lack of clay,but you MUST have access to Lime,some will argue you can find random spawned pieces of it around the world,this is true,but i would blanch at the thought of trying to sustain your needs in this fashion.
you dont need player stalls to buy nails,they sell em in the game shop stall but the cost is pretty steep,i personally would encourage you to build your own anything wherever and whenever possible,as regardless of other arguments this is going to be most profitable way to do it,period. same with leathers and things,if you can find/build/craft it yourself,thats going to be the cheapest and most efficient way to do it. also,be wary of trading with other players,as scamming is easy and commonplace. even the stalls are not 100% secure,as you may have read elsewhere they do not display "charges" on an item,so you can try to buy a multiple use inspirational,and when you receive it only has 1 use remaining. As to using outside resources like the nsuidara market,i personally don't do it,so the only fair advice i can offer you is this:do so at your own risk.
As far as "fair" pricing,there's no such thing. Some things are more valuable to some than to others,and certain people are after certain things at certain times.you're best bet besides the obvious (which is hit and miss studying of the various trades in forums and stalls trying to get an idea) is to form a couple friendships or at least business relationships with a few TRUSTWORTHY players,to build your own mini trade network of sorts. reasonable folk will try to give you a relative idea of somethings worth,and if you're friends they might sometimes compromise in your favor on price,to help your noobie butt out
Also,sometimes higher level players will pay you reasonable compensation for relatively common gatherables just to save themselves the time and effort of wandering around hunting a specific item.with some luck and timing these "mercenary" chores can fill up your early purses quite nicely.
As far as using "abandoned" bases,i dont discourage it,like you said it could help you get a huge jump at the start,but a few things to consider:
1) beds being slept in mean it may NOT be inactive,and established players are likely to be less than friendly to "squatters"
2)if it has a claim already on,even a tiny one,you arent going to be able to expand your own claim closer then 5 tiles from the existing one,thus effectively foiling your eventual expansion.
3)even if the upkeep has expired on a claim,to my knowledge it continues to function as normal with respect to black bile drain,braziers firing and so on,and you have to have the "Waste" skill to demolish it out of the way anyhow,so this is NOT going to be a viable option for you starting out,or even for quite some time...
4) if you DO find a suitable existing base to "repurpose" be advised that containers and equipment left outside are subject to decay,so your first goal after establishment will need to be running around repairing everything possible so you dont load a box with goodies only to have it disintegrate while youre offline and take the goodies with it...
Finally,as to "rushing" for a cotton economy,just don't do it. the only real lucrative money is in higher tier and purity output,which has to be built over time and careful maintenance. A compost and Loom arent going to get you rolling in the money right out the gate
in fact,a far more necessary build for any chance of success right from the start is a scarecrow,and that takes GLASS,so you're going to need your mining operation already running AND producing wrought (for crucible) or else buy from town (a glass pane in game stall is 350s)
I hope this advice helps at least in stimulating your thinking about various mechanics and variables that could be a difficulty to you,and how to surmount them. I'm happy to assist with whatever advice I can so feel free to post follow-up or message me directly with questions. (although be patient for reply,as I tend to spend more time in-game than here in Troll Land.)
This game is full of cowards. Don't fear the braggarts and blowhards,it's the ones who CLAIM to be your friends that will lure you into ambush and backstab you.....