Hard Drive Upgrade: Not needed really unless you need more space. I would be fine with this size.
It’s quite possible you could buy this iMac for about $600 and then just use it. If you needed more ram you could add 16GB for $100 so about $600 or so would get you a very nice iMac with a fast i5 processor and enough ram and a fast SSD already installed
This Apple MacBook Pro 15 A1286 2.53GHz Intel Core 2 Duo 8GB Ram 250GB HDD 10.6.8 tends to sell for about $250.00 now. That’s a pretty good price for a 2009 MacBook Pro with the following specs
It already has the ram maxed out to 8GB which is the maximum ram you can install in the 2009 MacBook Pro Models.
The only upgrades you would need for this model would be:
SSD drives make a world of difference in these MacBook Pros and the original drive in this is only 250GB anyway. If you replaced the hard drive with the same sized SSD drive you would not lose any space and yet have a much faster MacBook Pro.
You will need a new battery. You can buy a 3rd party battery for about $30.00 for this MacBook Pro.
If you swap out the hard drive for a faster ssd and add a new battery to this Mac you can have a very nice MacBook Pro for about $400.00 after upgrades.
The Apple MacBook Pro 13.3” LED Intel i5-3210M Core 2.5GHz 4GB 500GB Laptop MD101LLA sells for about $600.00
This 2012 non-retina Macbook Pro is a bit on the old side now but it’s still got a lot of life left if you added a few upgrades:
2012 MacBook Pro RAM
This MacBook Pro ships with just 4GB of RAM but it can accept at least double to 8GB with ease for about $50.00
2012 MacBook Pro Drive Upgrades
You have 2 options when it comes to upgrading the 2012 MacBook Pro Hard Drives:
Add a spinning hard drive to at least double the capacity to 1TB of storage if not more. This is a pretty cheap upgrade at about $50.00
Add a SSD Drive. This is much faster than a regular drive and although you don’t get the capacity of the spinner, you do gain a lot of speed making the MacBook Pro much faster. SSD Drives are about $100 for 256GB models and $200 for 500Gb capacity
Other 2012 MacBook Pro Upgrades
As this is an older MacBook Pro you might want to consider a few upgrades other than RAM and storage:
This MacBook Air from 2015 tends to sell for about $1000 (check price)
128GB PCIe-Based Flash Storage. Apple 13.3” MacBook Air MMGF2LL/A. 8GB of 1600 MHz LPDDR3 RAM. 1440 x 900 Native Resolution. 802.11ac Wi-Fi, Bluetooth 4.0. Main Features. 13.3” LED-Backlit Glossy Display.
There’s really not a lot of upgrades you can do for this MacBook Air.
2015 MacBook Air Hard Drive Upgrades
You can upgrade the MacBook Air’s Hard Drive to a larger storage capacity, but it’s not cheap with 256GB SSD Upgrades going for about $250.00 check price and 512GB SSD’s selling for about $350.00 check price
A few other upgrades to consider would be adding a new battery (not sure you need it in a 2015 model) or adding a monitor for more screen real estate.