Web Crawler help

[snippsat]

The make your error,size is a string.

>>> size = ''
>>> size.find_next_sibling('span')

Error:
Traceback (most recent call last):
  File "<string>", line 301, in runcode
  File "<interactive input>", line 1, in <module>
AttributeError: 'str' object has no attribute 'find_next_sibling'

Try to post better formatted HTML,Both CodePen and JSFiddle has Tidy HTML function.
One way to do it:

from bs4 import BeautifulSoup

html = '''\
<ul class="properties-list">
  <li>
    3067 JH Rotterdam
    <span class="item-sold-label-small" title="Verkocht">Verkocht</span>
  </li>
  <li>
    <span title="Woonoppervlakte">90 m²</span>
    <span title="Aantal&nbsp;kamers">4 kamers</span>
  </li>'''

soup = BeautifulSoup(html, 'lxml')
p_lst = soup.find(class_="properties-list")
span = p_lst.select('li > span')
print([item.text for item in span[1:]]) 

Output:
['90 m²', '4 kamers']