SF340 First Officer experiences HYD3 low pressure just prior to V1 during takeoff and continues. After takeoff the gear will not retract producing many cautions and warnings. After consulting the non-normal checklist (4 minutes) the gear retracts and the crew returns to the departure airport for a normal landing.

Narrative

I was the pilot flying executing the takeoff. Just prior to V1 we received ICAS caution of HYD3 Low Pressure. Continued the take off and retracted the gear. After trying to retract gear we got multiple cautions and warnings for gear disagree; nose door open; anti-skid inoperative. Tower gave us a call for a heading and over to departure and at this time Captain asked for vectors and to stay at a lower altitude for a possible return. Captain went into the non-normal checklists while still getting multiple warnings. As soon as Captain got to the correct page in the Flight Manual the gear began to retract. Captain guessed that the gear came up maybe 3-4 minutes after takeoff although the time was hard to judge. The Captain contacted Dispatch and Maintenance and we returned to land. No emergency was declared. I configured the airplane early in the approach. ATC did have the ARFF vehicles waiting for us when we landed although we did not request them. We parked at and had an aircraft waiting for us. We departed 1 hour total late and landed only 25 minutes later than scheduled. The Captain informed the 5 passengers what happened. The crew did as trained and there were no issues.