Thats kinda relative though depending on your weight and his...
Im a big guy 6'0, 190 So I have more weight to push up then others. Whereas you might have someone who is 5'6 and like 125 who can put pushups away.
Now on the other hand I have no problem putting away 70 or so in one session, but that came with endurance and regular training. It sounds like the OP is starting from square one.. So they'll get there. One suggestion I can offer is something a SEAL friend told me. Do what you know is your max, and add 1 or 2 on each time.. And keep building from that...
Also got to take the age factor into consideration.. I am 26 so that 70 looks alot better on the scale for my age then it would for lets say a 20 year old.
EDIT: I wanted to add another trick for the OP just something to build on... maybe take a day or two out of the week and make them 100 push up/sit up days... Basically what that means is knock out 20 of each here and there periodically throughout the day... Just get out of the head? hit the deck. Just woke up? hit the deck. Gangland coming on? hit the deck. It will build up some strength as well as give you some mental motivation knowing that you are one of the only people that day that did 100 push ups and sit ups.. I know you said you do not have a gym membership, but just to give you an example I do it sometimes in the gym with that and dips. Kinda gives me peice of mind knowing I've done more then most in the gym that day
Yeah i've started doing the 100 pushup thing during the day on my work days. My paster (former army enlisted) told me to start doing that. I'll add in the +1 to max thing in there too. Thanks for the tips