I cannot recommend that you buy a quality lawnmower highly enough. Yes, you will pay for it but it is SO worth it when you count the time and effort saved in having a durable and reliable product.
I myself use a Snapper rear engine riding and IMO Snapper makes a very fine product.
Have a read,
http://www.fastcompany.com/magazine/102/open_snapper.html
that article explains why Snappers are not sold in Walmart and goes through some of the manufacturing processes.
http://boards.straightdope.com/sdmb/showthread.php?p=7830047#post7830047
I put a new thread in MPSIMS, as an update to this thread. I have indeed repaired the Weedeater lawnmower. For the record, those who told me to learn small engine repair, I do have some of the skills needed to fix smaller problems, but if you had been there, you would have thought the block was cracked. The Briggs and Strat engine has a plastic cover over it to keep dust and such out, that prevented me from easily finding the missing bolt. I just really needed to vent, I was just so pissed thinking the motor was blown.
Repairing the mower may not be necessary. What have you been doing for maintenance for those mowers you’ve used for more than one season?
Clean/replace the sparkplug, clean/replace air filter, gas filter,maybe even the oil filter. And change out the oil at the beginning of each year. Simple stuff like this will keep almost any mower running for a long long time.