>>1578618getting into cycling as an adult is more complicated than you seem to think, even walmart bikes cost a couple of hundred, quality bikes cost more
>>1578668quality brands have at least 4 different frame sizes per model and then you can just follow the size chart based on height and with some rules of thumb like rounding down the size on a road bike if you're between sizes, on a mountain bike you might have a preference to round up instead but it can go either way