In Terraforming Mars, during the Research Phase, when buying patent cards, can you first look at the cards and then decide how many to keep?

Terraforming Mars, at the Research Phase at the start of each generation: When each player draws 4 Project Cards, do the rules allow first carefully reading all 4 cards' effects and costs, and then choosing to buy 0 to 4 of them (paying 3 M€ each), or must it be blind draw and blind buy? If you don't have enough money for 3 per card, can you still keep cards?