Bike/wheel size for a beginner

There are several bikes with 650 wheel and sloping frame. many Felt "F", "S" and "SR" bikes have 47cm frames with 650 wheel as do Trek 1000/1500 WSD 650 43/47cm bikes.

A 4'11" friend bought a Merida Road 240 today, it has 650 wheels, she looks good on it.. I am looking for a 52/52cm road bike with 650 wheels too and I am 5'7".

I have a triathalon bike with 650c wheels and a standard 700c bike and am 5'8". Both ride fine for me, the 650c spare parts and comsumables are not as common, range is restricted and prices are higher to boot 😠 but it is tough and stays true over some rough roads, the shorter spokes are supposed to make the wheels 20% stronger and a bit lighter, ie good for tri's. The 700c tubes and tires are cheaper and easier to sell and buy on ebay. At 5'6" would be suprised if a standard frame with 700c wheels could not be found to fit you, cannondales ( and others )have 50 and 52 cm frames that would be close to the right range for your height and inseam, test ride is the way to go.
I find sloping frames cramp the water bottle access, a minor point for some but in hot weather a pain.
Take your time to select and keep researching.

KarineM said:

As I'm thinking of buying a proper bike to replace my supermarket one, which is too small. I've been reading lots of aricles on sizes and materials. I think I've got the gist for the top tube length etc. But as I'm only 5'6" with a 31" inseam, I've been wondering about the possible advantages of 650 wheels or sloping frames. Are there any? I wouldn't trust a bike shop salesman to advise me.

What do experienced bikers think?

I'm about the same height as you and had a Giant OCR3. The frames start at 44cm and it was a perfect fit for me. The wheel are 700c and they have sloping top tubes, but never had a problem getting water bottles in and out. They're pretty damn good bikes in my opinion.