The $2,500 deposit will go a long way toward a down payment on a truck that you will own. If you need to pay Penske $675 per week in addition to $0.12/mile then you would pay them over $1,000 per week if you run 3,000 miles. $675+ (3,000*.12) = $1,035 per week or $4,150 per month.
You can buy a box trailer for $3,500. If you have $2,500 for a deposit on a trailer you could probably have enough to pay cash for a trailer that you own. $150 + (3,000 miles*.05) = $300 per week or $1,200 per month.
That means if you rent both a truck and trailer from these people you will pay out $1,335 per week or $5,350 per month and you haven't bought fuel or paid your insurance. If you add the deposits on both pieces of equipment you will spend $11,350 your first month on equipment that you will never own.
You could pay cash for a truck and trailer in 6-8 weeks for what you will spend on deposits and rental and have equipment that is free and clear.