The thing about digital photography or videography is that it's more than just camera technology, it inevitably evolves into an art form. It's not like owning the latest and greatest smartphone or gaming laptop where specifications and build quality are enough to guarantee a good experience or result. When a person becomes passionate about taking photos, the technology takes a backseat and flexibility becomes the utmost importance.
Personally, I have more cameras and lenses than I have fingers and toes and that's as an amateur hobbyist — I've never earned anything through photography. It's just some years of learning and growing with different processes and techniques. To photographers in general, a high end body with a kit lens is a highly undesirable combination. I can probably count on one hand how many photos I took with a kit lens throughout my entire life. I quickly preferred a multitude of fast aperture non-zoom lens as an alternative to the super pricey f/2.8 zooms. Kit lenses are more useful to me (and most other amateur photographers I know) as paperweights.
Restricting yourself to an A7 IV and kit lens is like having beautifully handmade exquisite paintbrush from the mountains of Japan, paired with Camel water colours. When the better alternative would be a wondrous set of deep acrylic paints imported from some exotic place with a decent locally made brush (a lesser costing body but with a nice selection of lenses). If extra lenses are not possible in your budget, then a camera with a high quality built-in lens like the RX100 series or the ZV-1 is a lot more flexible than an A7 IV with a kit lens even though the A7 IV has a far more superior sensor.
Another thing to consider, it may be better to split your needs into multiple cameras — some years ago, it was believed that using a still camera for video recording degraded the sensor enough to notice a difference in the sharpness of still photos. I'm not sure if this is still conventional wisdom or if sensors have evolved enough to prevent this from happening.
Lastly, cameras are rarely investments unless if it's something like a Leica — they cannot be reliably serviced or repaired out of warranty, parts eventually become unavailable and first party batteries/accessories would quickly disappear. Expect about maybe two to three years of daily use from whatever you purchase today, though it's more likely you'll want something better or different in less than a year, no matter what you buy today.