Any business requires initial investment. Both the cattle and crops will take some initial setup expense. However that initial investment doesn't need to be paid back the first year - amortize them over time and they can have a very good ROI.

My suggestion would be to do as others have said, do both. You can shift acres back and forth from one to the other as you get going. I would stick with your 34 heifers for now. Figure on buying a good registered bull. Put up a good perimeter fence around your pasture land with wide gates in corners to provide access to and from the crop land in the future.  You have a lot of possibilities for grazing corn stalks after combining.

I would not put a lot of money into buildings other than you need a shop/shed for you, not the cattle.

How many head do you want to end up with? What about winter feed/hay? Can you hire someone to make hay on part of your crop acres for your winter needs?

You will need a basic handling facility - corral/tub/lane/chute with a scale in there somewhere. You need good year-round water points. Work with someone such as Ben suggests on the layout.  If you have a good perimeter fence you can do semi permanent interior fences on the 100 acres and then moveable hot wires on stepins for rotational grazing. Also - in your cattle operation, what is it you are aiming for as an end product? What are you going to sell? Weaned calves? feeders? fats? Freezer beef? All of the above?

If you have a full time job off farm you want to be realistic on how much you can accomplish this year.  I would maybe consider still hiring out the crop work on shares for a year or two and focus your efforts on the cattle. There is a learning curve there. Make sure your shares agreement covers application of fertilizer/lime etc.

Actually 300 a is a very nice size. On the 200a of crop land you could eventually work towards doing it all yourself except maybe hire a neighbor to do the combining. That area is good for a wheat/bean/corn rotation. But ease into that.

Eventually here is what I would think would be adequate in your system in your area: 125-150 hp tractor with loader and Gnuse hydraulic top  link, (the 4020 will come in handy as a 2nd tractor), 15 ft 6r30 mounted Pluribus strip till bar with liquid fert system (saddle tanks on tractor?) for spring strip , 15 ft 6r/30 mounted, late model JD or Kinze planter with row cleaners and Curvetines(for your corn and DC beans), 15 ft notill drill (several possibilities) with small seed box (for your wheat and interseeding pastures), a mounted or pull type sprayer, a mower, preferably flail type, a drag, maybe an Aerway.

May sound like a lot but it would pay for itself fairly quickly in both cattle and crop operations. With an outside job I would get good equipment unless you like totally rebuilding 7000 planters. Even then you end up with a rebuilt 30 year old 7000 planter. The planter and drill are the two most important pieces of equipment on the farm.

Hire hay making and combining. You can get a fertilizer cart from the dealer and spread your own dry P & K. N for corn can be put down with the strip till bar.

You have a great opportunity there. I would be careful to start gradually.  Best of luck.

Jim