you start with only one frame (the one you chose at start) you have to make your 2nd warframe
(by farming BPs form a boss) most bosses drop 1 type of frame's BPs exp:jackel drops rhino parts BPs after that you make the parts in your foundery (they take 12 hours) then you buy your frame's BP at market... it uses the parts you made + 1 orakan cell and takes 3 days to make
you can reset your account theres details how on warframe's offical site (dont know i didnt do it or want too)
you start with 2 warframe slots (one open one for the frame you start with) and 4 weapon slots and 50 platinum... 50 platinum is enough to buy eather 2 warframe slots or 1 frame slot and 4 weapon slots.... or supercharge for a warframe or weapon(they coast same as a warframe slot 20*
i recomend 1 warframe slot and 4 weapon slots but thats me
also you can sell your old warframes and weapons to clear up new slots to use