It's good idea. If you want to make the limit charaters when adding new property in the frontend, you can edit file
components > com_osproperty > classes > listing.html.php
lint 2694
<input type="text" name="pro_name" id="pro_name" value="<?php echo $row->pro_name?>" size="50" class="inputbox" /> <span class="required">(*)</span>
In this tag, you can add attribute maxlength to limit the characters entered.
Good luck !
Dam