The very large production numbers and strong aftermarket parts support make the MGB a superb entry-level, low-stress sports car. It was built in the days when cars still had ignition points and grease fittings; any reasonably deft enthusiast with a copy of the factory manual can maintain one of these cars.
MGBs come in four main groups: those with three main bearing engines built from '62 to '64, those with five main bearings ('65 to '69), emission-controlled cars ('69-'73); and rubber-bumper cars ('74-'80).
Their stiff unit structure, replacing previous MGs' body-on-chassis construction, combined with an all-iron 4-cylinder pushrod 1800-cc engine, independent front suspension, solid rear axle on half elliptics and front disc brakes, made this the best MG yet when introduced in '62. An optional overdrive became available in 1965 and a new full-synchro gearbox in 1967.
Watch out for slap-dash color changes. The B is painted inside and out like an XKE or Austin-Healey. A thorough color change would require complete disassembly, a process not supported by the modest value of the MGB.
Wire wheels are attractive, but can't stand up to the stress of spirited driving, especially when shod with modern performance tires. Modern alloys do a better job.
Concours-winning cars can reach $10-12,000. A restored car is a huge bargain and will cost about half the price of doing the job yourself. Drivers in tidy condition run the range from $5-7,000, with preference given to pre-1968 cars. 1969-73 B's are a bit cheaper because of their emission-controlled engines, (although now in many states the engines can be backdated to earlier, more powerful specs). The rubber-bumper cars built after 1973 commonly bring 40% less than their earlier (and more attractive) cousins.
It is possible to find driveable chrome-bumper "project" cars for $3,500. This is the most fun per dollar for the enthusiast with a desire to discover the joys of hand cleaner. However, don't go too far with the restoration. Anything beyond a few suspension bushings, a valve job, seat covers and some brake work will put you close to the price of a restored car.
If you don't want to get greasy, in the under $7,500 range, a chrome bumper B in presentable condition is hard to beat for ease of ownership and high resale value.