I second the recommendation for buying a used 70's or 80's bike.

IMHO a good bike of that era will last you a lifetime, be comfortable, cheap, tough and fast. Feel free to upgrade whatever components you like - I recommend new brake pads, new chain, and (only if it needs them) some 700C wheels of your choice.

You could also buy an old bike like this, and fit a new groupset to it.

PS: Congratulations on your 10,000,000th thread.