Hey there,
Here's really what you need to figure out before doing anything else.
The cheapest place you're going to find the S3 is at the manufacturer's (Bitmain) website.
Right now, the cost for an S3 is .58 BTC per uniit
Question you need to figure out is: how long (if ever) until these 2 miners give me back 1.16 BTC + my related costs.
That's it, before you figure that out, do not pass go.
Also, to the question of using 1 PSU for a PC & your miner:
No offense, but, if you're even contemplating this, I would definitely hold off and take a moment to read through the mining how-tos here before jumping into anything. I know how it is starting on a budget, but there's a right way and a wrong way - and that is the wrong way.
A- My plan was to start with a small investment, buying one up-to-date miner only, then let it run for a few days... even if i need to keep the PC on during this time.
The small investment plan is needed because:
1- am not sure if the miner will be cleared at the customs when it arrives, coz i've had such an experience before.
2- am not sure how my ISP' network is configured. if for some reason i cannot mine properly then it is a dead end for me, since almost all companies and services here are in their infancy and nobody knows what they are doing.
If everything went well, then i would get more miners along with power supplies and a UPS (yes i need one).
B- For buying options: well i do not have any BTC yet, and either case, my only option to buy hardware is through online retailers.
the S3 is about $320 on Amazon now. are there better options?
C- does these parameters look normal? (yes free electricity)
https://i.imgur.com/PKtZKFz.png