I had some electrical wire ran in my basement by a friend. He used 12/2 (or 20 amp wire) but only used the standard 15 amp outlets. Is this going to be OK? It is not connected to the breaker panel yet. I would think I NEED to use a 15 amp breaker, but when I sell my house soon, the home inspector will notice the wire in the panel and make me change it to 20 amp breaker I think? Any chance of my outlets melting while using the 15 amp outlet?

You can put a 15 AMP breaker in and run 12 AWG, it is done quite commonly. You can also leave the 20 AMP breaker in and use the 15 AMP receptacle, that is code allowed.

I do not think you can use a 15amp breaker while using 20amp wire such as 12/2... Any home inspector will make you change from a 15amp to a 20amp breaker I think?

Ironbull, you do not think so, but we DO KNOW so.
In the US, 15A duplex receptacles ARE allowed on 20A circuits.
I can throw all sorts of code citations at you if you like.

What do you think the danger is? Are you aware that 15A receptacles are rated for 20A feed-thru?

Thanks guys for clearing that up for me. I appreciate your time!

Nope. The breaker is the limiting item, not the wire. In fact, if you run a long wire lead, say 50ft, you are much better to run 12 instead of 14 and use a 15 Amp breaker. That way, you have little voltage drop.

NEC 210.21(B)(1) says that a single receptacle on an individual circuit has to be the same as the circuit.

But NEC 210.21(B)(3) states that two or more receptacles on a circuit branch (not exceeding 50 amps) needs to follow Table 210.21(B)(3) and according to the table, a 20 amp circuit with 2 or more receptacles can use 15 or 20 amp receptacles.

So a 20 circuit would always use 12 gauge wire and if the NEC states you can use 15 amp receptacles on a 20 circuit then it proves the point that 15 amp receptacle can be put on 12 gauge wire. Sometimes a larger wire is needed on long runs to prevent a voltage drop. So a 12 gauge wire may be used instead of 14 gauge to prevent a voltage drop.

Note you can not put a 20 amp receptacle on a 15 amp circuit. Nor can you use 14 gauge wire on a 20 amp circuit.