If a community faces a poor economic climate, its residents will be unlikely to support homeless people. Naturally, they will focus on providing for their own needs, with little resources left over for charitable giving. By striving to improve the economy overall, we can increase donations to the homeless and thus reduce this problem.
There is considerable evidence that homelessness worsens a nation's economy, making it unlikely that substantial economic growth will occur alongside homelessness. 
[P1] Financial prosperity makes people more likely to support charity.