Hi i would like to purchase a new mac/computer and want to find out whether this mac would be able to run sims 3.
Its a Imac 2007 20"
Not sure what specs to include so i will just put all of them:

Product Identifiers
Brand Apple
Product Family iMac
Model ID iMac7,1


Processor
Processor Type Intel Core 2 Duo
Processor Speed 2.4 GHz
Number of Cores Dual-Core

Motherboard
Video Output Interface PCI Express
Motherboard I/O Ports FireWire (IEEE1394a) x 1, FireWire (IEEE1394b) x 1, RJ45 Lan Port x 1, USB 2.0 x 5
Bus Speed 800 MHz

Display
Screen Type Flat Panel LCD
Screen Size 20"

Hard Drive
Hard Drive Capacity 320 GB
Hard Drive Rotation Speed 7200 RPM
Hard Drive Interface Serial ATA II

Memory
RAM Technology DDR2 SDRAM
Manufacturer''s RAM Capacity 1 GB
RAM Supported Speed 667 MHz
RAM Memory Slots Qunatity 2 x 240 Pin DIMMs, 2 x SODIMM
Installed Cache Memory 32 KB
Max. Cache Memory 4 MB

CD / DVD
Optical Drive Type DVD±RW Dual Layer/CD-RW
Optical Drive Read Speed 24x (CD), 8x (DVD)
Optical Drive Write Speed 24x (CD), 4x (DVD+R DL), 4x (DVD-R DL), 8x (DVD+R), 8x (DVD-R)
Optical Drive ReWrite Speed 16x (CD-RW), 6x (DVD-RW), 8x (DVD+RW)

Video
On Board Graphic Processor ATI RADEON HD 2600 PRO
Max. Video Resolution 1680 x 1050
Installed Video Memory 256 MB
Video Input Type Video Capture Adapter
Video Outputs 15 Pin D-Sub VGA port x 1, Composite x 1, DVI x 1, Mini-DVI, S-Video x 1

Audio
Audio Input Integrated Microphone, Line In (3.5mm), Microphone, Optical Digital In, SPDIF in
Audio Output Headphones, Line Out, Optical Digital, Optical Digital Output, Sound card, Speaker(s)

Networking
Data Link Protocol AirPort Extreme, Bluetooth, Ethernet, Fast Ethernet, Gigabit Ethernet, IEEE 802.11a, IEEE 802.11b, IEEE 802.11g, IEEE 802.11n
Networking Type Bluetooth, Integrated 10/100/1000 Network Card, Integrated Wireless LAN

Dimensions
Depth 18.8 cm
Height 47 cm
Width 48.5 cm
Weight 9.1 kg

Miscellaneous
Form Factor All-in-One
Release Date August, 2007
Exterior Color Silver, Black
Other Features Built In Web Camera, Infrared Remote Control

How many/which EPs are you hoping to play? I can already tell you that if it only has 1GB of RAM, then even the basegame is going to run like crap; but 1GB of RAM seems incongruent with the CPU and GPU you've listed, so you might want to double-check that that info is correct.

Oh, i have all eps and only master suite, high end loft, 70s 80s & 90s stuff, outdoor living and fast lane

Then the answer is definitely not. The three most important things for TS3 performance are CPU, RAM, and graphics card, and that computer doesn't meet the minimum requirements for any of them. Game Help:TS3 System Requirements^wiki
You should also be aware that TS3 suffers from even more bugs on Mac than it does on PC, including many CC hairs not working.