Well I think it is a time for a bit of reality check.
1) If going OFF GRID meaning that you are NOT pushing anything to the grid BUT may use Grid Power as an AC Input or charging batteries.
This requires less permits if any (depends on where you are) and is generally much less hassles AND COST (permits, inspections etc = $$$).
Many Insurance Companies will still require electrical inspections and may have other requirements for coverage. Some companies are "Battery Shy" simply because they are stupid and stuck in historical invalid info. Boy do we see some stupid come from insurance co's & local "Governing Mentals".
2) Grid Connected for Feed-In to Grid is far more complicated because you will need inspections & certified equipment as well as permits & such and THAT CAN EASILY ADD 25-40% ON TOP OF COST. Largely due to Certification requirements & if they insist on Commercial Installations you are paying the Big Bux for that. AGAIN - Depends on WHERE you are and BE READY FOR DUM-DUM !
The Good News:
Plan FORWARD and build with an eye towards the future to grow the system. With LFP Batteries, you can add more later if/when wanted WITHOUT ILL EFFECTS unlike the old Lead Acid battery days ! So YES you can add batteries later without any loss. You can add more solar or Inverter in parallel as well as your needs/wants grow.
MOST IMPORTANTLY - DO NOT BUY ANYTHING TILL YOU HAVE A SOLID PLAN !
Know "what" direction you are going in.
Know what the Local/Regional rules & requirements are (both ON & OFF grid options)
KNOW What your Insurance Company will need / want ! (they can be a real PITA)
When you KNOW what is legal/not and what you can do THEN start considering the hardware.
Be sure to know what your usage is / will be and then add 20% ON TOP ! (everyone ALWAYS undershoots)
Be CERTAIN to select equipment that meets TODAYS Needs but that can handle the future expansions.
BE CAUTIOUS !!! While some equipment may seem a good deal with lots of features etc, it's best to understand it ! This takes a while. COST is NOT a measure of Quality & Cheaper does not mean good value. AIO's may seem good idea & deal and can be BUT NOT IN ALL SITUATIONS (quite a few actually).