I gave this guy a price for my domain and he wrote back saying they are willing to buy if: they can pay one half by check at which time, the transfer process is to begin.

Upon transfer completion, they will pay the remaining balance.

Now my feathers are ruffled! do they think they can get away with such a payment plan where they have the advantage?

Or, am I wrong?

Thanks,
fewcoin

Use Escrow.com and have the full payment made in the process.

As radistar said, use a third party escrow and secure payment before allowing the name to be released.