It looks like an Eastern Redbud. Compare close-ups of the flower.

Here is a link that might be useful: Photos and Links

looks like a crabapple to me.

I agree, crab apple. The striking thing about it is the semi weeping habit. Ask the neighbor where they got it, if they don't know, take your photo the the local nursery and see if they can help. Or go the the Longenecker Gardens at the Arboretum and see if they have one that matches. They have the largest collection of flowering crabs in the Midwest.

Steve

One of the local landscapers here has a very nice specimen of a similar if not the same tree as you neighbor's tree.

Check out the link to see if it's the same.

Here is a link that might be useful: Louisa Crapapple

It might be a Weeping Cherry Tree that someone pruned. Mine has the branches inches of the ground. Some people don't like the fact that no grass will grow undstory if the branches reach the ground and hack them up. Mine bloomed pinker this year and had more blooms than ever before. Like I said before a close-up of the flower will tell all.