Tsarnaev’s younger brother never seemed strapped for cash, according to people who knew him at the University of Massachusetts Dartmouth where he was a sophomore. But Dzhokhar Tsarnaev was a scholarship student who earned spending money by selling marijuana, say three people who bought drugs from the 19-year-old.

Even the explosives they allegedly set off at the Boston Marathon a week ago turned out to be crude and inexpensive — likely built from ordinary kitchen pressure cookers, nails, and other household items from instructions available online. Each bomb may have cost less than $100.

If the brothers had outside financial or technical support for their deadly attack on the Marathon, it certainly isn’t reflected in their lifestyle or their weapons. The picture that is emerging is more like terrorism on a budget, consistent with reports that Dzhokhar Tsarnaev told interrogators from his hospital bed that he and his brother acted alone.