The condition is that a man should be just with all of his wives, and justice includes the expenses as well as spending time and sleeping overnight with each of his wives equally, and each has as much allowance as the other.
(You will never be able to maintain ˹emotional˺ justice between your wives—no matter how keen you are. So do not totally incline towards one leaving the other in suspense. And if you do what is right and are mindful ˹of Allah˺, surely Allah is All-Forgiving, Most Merciful.) An-Nisa 4:129
فالشرط أن يعدل الرجل بين النساء و العدل يكون في النفقة و المبيت فيبيت عند كل واحدة من الزوجات بقدر ما يبيت عند الأخريات و لكل واحدة منهن نفقة بقدر الأخرى.(وَلَن تَسْتَطِيعُوا أَن تَعْدِلُوا بَيْنَ النِّسَاءِ وَلَوْ حَرَصْتُمْ ۖ فَلَا تَمِيلُوا كُلَّ الْمَيْلِ فَتَذَرُوهَا كَالْمُعَلَّقَةِ ۚ وَإِن تُصْلِحُوا وَتَتَّقُوا فَإِنَّ اللَّـهَ كَانَ غَفُورًا رَّحِيمًا ) النساء 4: 129