Why do Marilla and Matthew decide to bring an orphan boy to Green Gables?

The brother and sister decide to bring an orphan to Green Gables because Matthew needs help with the farm.

‘Well, we’ve been thinking about it for some time—all winter in fact,’ returned Marilla. ‘Mrs. Alexander Spencer was up here one day before Christmas and she said she was going to get a little girl from the asylum over in Hopeton in the spring. Her cousin lives there and Mrs. Spencer has visited here and knows all about it. So Matthew and I have talked it over off and on ever since. We thought we’d get a boy. Matthew is getting up in years, you know—he’s sixty— and he isn’t so spry as he once was. His heart troubles him a good deal. And you know how desperate hard it’s got to be to get hired help. There’s never anybody to be had but those stupid, half-grown little French boys; and as soon as you do get one broke into your ways and taught something he’s up and off to the lobster canneries or the States. At first Matthew suggested getting a Home boy. But I said ‘no’ flat to that. ‘They may be all right—I’m not saying they’re not—but no London street Arabs for me,’ I said. ‘Give me a native born at least. There’ll be a risk, no matter who we get. But I’ll feel easier in my mind and sleep sounder at nights if we get a born Canadian.’ So in the end we decided to ask Mrs. Spencer to pick us out one when she went over to get her little girl. We heard last week she was going, so we sent her word by Richard Spencer’s folks at Carmody to bring us a smart, likely boy of about ten or eleven. We decided that would be the best age—old enough to be of some use in doing chores right off and young enough to be trained up proper.